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FireFox 3 and Static File Caching Problems


:P
On this page:

FireFox 3.0 apparently is much more aggressive in caching content than previous versions of FireFox. While this is good for performance in many situations I've noticed that this is seriously becoming a problem in some of my applications where support files like scripts and CSS files get updated and FireFox doesn't recognize those changes. The problem appears to be that FireFox is not sending the required 304 request to check for last-modified headers that are typically used for static files.

The latest example is my (ancient) Message Board site which I recently updated by reducing the HTML and externalizing most of the inline styling into an external CSS file that previously existed. Today I'm waking up to 10 messages from visitors that the the formatting of the message board is completely mangled. Apparently the CSS file changes are not being picked up by FireFox 3.0 and so users see the new dynamic message board pages, rendered against the old CSS styles cached in the browser. Thankfully I did this over the weekend and so the cacophony of disgruntled visitors was only minor.

The updated CSS file is there on the server. IE, Opera and Safari and even FF 2 all work fine - only FF3 fails to refresh the CSS for clients because apparently it's not detecting the last-modified date for the static resource. Even pressing Refresh doesn't fix this and even FireFox's 'hard' Shift-Refresh doesn't do the trick if the CSS is already cached.

Part of the problem here is that the app is frames based. Shift-Refresh should in theory force a refresh of all resources (and it does usually), but in the case of this frames based layout it doesn't. The only way to force the CSS to refresh that I found is to Ctrl-Click one of the links and force into a new frame, then force a Shift-Refresh in the new window. Intuitive, eh? Oh, or you can clear the browser cache! Yeah - that's what I tell 'em! <g>

But it's not only this CSS that suffers. I've also had issues with AJAX related static JavaScript files served from the server that also didn't work with the same caching issues. This is even more insidious because you can't see the problem except that potentially your app will fail now because the application's client application data is not up to date.

Again only a Shift-Refresh usually solves this problem. While this is fairly painless to do in the dev environment (it's become a habit already to Ctrl-Click) this is a big problem in production environments since you certainly don't want to tell your visitors to 'just Ctl-Click and things will be cool'.

It appears that the problem is vaguely related to this post:

With Firefox 1 and 2, “Cache-control: no-cache” accomplished this goal. I’ve spend the last several hours trying to figure out how to prevent Firefox 3 from caching my pages, with no luck. It completely ignores “Cache-control: no-store, no-cache, must-revalidate” and every combination of values for the “Expired:” header that I can think of, in blatant violation of RFC 2616 (14.9 and 14.21).

This post also mentions how you can modify your cache settings. While this works this is hardly a solution for end users.

Last-Modified Headers not working properly in FF3

The issue described in the post is in regards to caching, which is a little different actually than what I'm experiencing here, which has to do with the last-modified header that static files use. Web Servers serve static files (like CSS and scripts) from disk and they tend to serve this data with a last-modified header which the browser is supposed to respect. When requesting data again for a page that when originally loaded the browser is supposed to fire a 304 request to see if the content has changed.

Here's what the 304 response looks like in Internet Explorer with Fiddler enabled. IE fires the hit to the CSS file every time as a 304 request which looks like this:

GET /wwThreads/wwthreads.css HTTP/1.1
Accept: */*
Referer: http://www.west-wind.com/wwThreads/head.htm
Accept-Language: en-us
User-Agent: Mozilla/4.0 (compatible; MSIE 7.0; Windows NT 6.0; Trident/4.0; SLCC1; .NET CLR 2.0.50727; Media Center PC 5.0; FDM; .NET CLR 3.5.21022; .NET CLR 3.5.30729; .NET CLR 3.0.30618; .NET CLR 1.1.4322)
UA-CPU: x86
Accept-Encoding: gzip, deflate
If-Modified-Since: Sun, 31 Aug 2008 09:37:26 GMT
If-None-Match: "20d7b72d4dbc91:0"
Connection: Keep-Alive
Host: www.west-wind.com

 

HTTP/1.1 304 Not Modified
Last-Modified: Sun, 31 Aug 2008 09:37:26 GMT
ETag: "20d7b72d4dbc91:0"
Accept-Ranges: bytes
Server: Microsoft-IIS/7.0
X-Powered-By: ASP.NET
Date: Sun, 31 Aug 2008 20:04:11 GMT

If the content were modified the server would respond with a full 200 HTTP response. So if I go in and modify my CSS file and hit the page again, IE will properly detect the change.

FireFox however, doesn't appear to fire the 304 at all. I've hooked up Firebug and the CSS files don't show up at all. Not trusting the FireBug network tracing I also hooked up FireFox to Fiddler and lo and behold it too shows that FireFox is not firing the 304's to check for updated files. When loading pages - even with Ctl-Clicking - I don't see the CSS files loaded which explains why the pages render all mangled. In my frames page even browser Refresh or even a Shift-Refresh doesn't cause the frames to reload their content or fire 304s to check for updates - all the static content is simply not accessed at all.

For example, if I start up FireFox fresh and navigate to my site and hit one link here's what Fiddler shows:

NoResources

Notice there are no other requests to any support resources - images, CSS etc. No checks for 304's. Here's that same trace with Internet Explorer:

IEResourceChecks :

and you'll notice all the 304 hits to verify resources. Now using Shift-Refresh in Firefox will force FireFox to refresh all those links explicitly and load them, but this isn't the expected behavior. The whole point of last-modified and 304s is to be able to detect changes to static resources and apparently FireFox doesn't play along here.

 

Frames

Ok, frames are so passé but as I mentioned the app I'm actually dealing with uses frames and the problem there is that a Shift-Refresh on the parent frame isn't enough to force the individual frames to refresh. In fact, I'm not really sure how to force FireFox to refresh an individual frame. The only way I've been able to do this is to load one of the frames by shift clicking into a separate window and then doing a shift-Refresh to force the stylesheet to reload. After that all's well because that updates the cache globally.

Refresh should be Refresh

What's worse though is that in FireFox 3's default configuration even clicking the Refresh button will not force 304s. Apparently the Refresh button behavior has been changed to only re-run the last request EXACTLY in the same mode it was run. So if you did a Shift-Refresh on the last hit, it will repeat that behavior. If you did a plain link click that will replay exactly and so on. There's no longer an explicit reloading of resources which is now delegated to Shift-Refresh and which no 'typical' user will think of.

The FireFox Refresh button's Refresh behavior is pretty lame. Having an easy way to force pages and all related content to reload is key in a browser environment where the underlying resources may frequently change on the server. Between the refresh and last-modified issues described FireFox 3.x is becoming a bit shaky for the stability, especially for applications that are rich in client side styling and script behavior. It's not uncommon for my apps to update CSS or script content several times a day and there's now a good possibility that these changes may not match changes in the underlying application that serves non-static content. This has bit me quite frequently now during development when refreshing pages and expecting to see update content only to find that things like Script files have not refreshed and a few times in production with customers complaining.

One temporary solution might be (thanks to Steve Black for the hint) to force the CSS references in pages to refresh by changing the URL slightly. Like

<link  href="wwThreads.css?i=1" rel="stylesheet" type="text/css"/>

The additional querystring will force even FireFox to refresh the data. But that's one heck of a hack. But I may have to resort to this because nothing else works reliably at this point.

So... has anybody else run into this in their applications? In searching around the Web it doesn't appear that there's much talk about this issue - I didn't find anything related to last-modified and a few discussions - which are related - to caching and back button and refresh behavior. It looks like Firefox is trying to be too agressive in caching. Sure, caching is cool for performance, but not if it's at the cost of stale content.

Posted in ASP.NET  HTML  

The Voices of Reason


 

Mike Gale
August 31, 2008

# re: FireFox 3 and Static File Caching Problems

I've had a surprising number of "did you upload that file" queries in the last two weeks.

This probably explains what's going on.

Thanks for exploring this.

Now we have to hope that this make / dumb decision gets fixed soon.

Shaun Kester
August 31, 2008

# re: FireFox 3 and Static File Caching Problems

Does changing any of the IIS settings for expiration and caching seem to help?

Rick Strahl
August 31, 2008

# re: FireFox 3 and Static File Caching Problems

@Shaun - I don't think this is a server header output issue since IIS should and does send static file content with last-modified headers. The timeout is fairly large, but that really shouldn't matter - the client is supposed to check for changes and FF doesn't check back as it should.

I did change the cache policy in IIS now so that it expires content daily now, but this isn't going to help existing visitors who have the content already cached.

Nicholas
August 31, 2008

# re: FireFox 3 and Static File Caching Problems

I posted a Twitter about this, after running into it on a major project. It makes developing with FireFox 3 a pain in the arse, since you're constantly refreshing. We adopted the "solution" of putting an extended querystring on the css/js includes, with a version number. Not ideal, but it's worked so far.

FireFox also has an annoying behavior (I call it a bug)-- if you have a web form with text boxes, select boxes, etc. and hit "refresh", the state of those form elements are left however they were set prior to the refresh. To force them back to true defaults, you have to ctrl+shift click the refresh button. Really stupid, and led to an hour or so of development time lost, thinking my app. was misbehaving.

scott
August 31, 2008

# re: FireFox 3 and Static File Caching Problems

We have a server control that handles all of our external css & js references and automatically appends the assembly version in the querystring ie. styles.css?1.0.112. This also ensures content hosters like akamai will get an updated version onto their caching servers.

Steve from Pleasant Hill
August 31, 2008

# re: FireFox 3 and Static File Caching Problems

Well, it used to be the joke that it took Microsoft 'til version 3 to get it right. Hopefully Firefox is not making it version 3 to get it wrong.

I get prompted every day or so to update -- but I keep holding off...

Rick Strahl
August 31, 2008

# re: FireFox 3 and Static File Caching Problems

@Steve - just heard from a couple of other users that are seeing the same behavior with FF2. It's possible that for me I haven't run FF2 in so long that the caching didn't apply.

I experimented around a little more trying other sites: Google, Microsoft, Yahoo - all of the sites are exhibiting the same behavior with FireFox: no 304's to check modified dates. FF appears to only wait for Expiration before it reloads.

Mehfuz Hossain
August 31, 2008

# re: FireFox 3 and Static File Caching Problems

Hey, while i was checking www.flickrmvc.net, my LINQtoFlickr Flickr site, i found this issue for Firefox FF2 or FF3. I have manually updated the CSS version, image version etc everytime i update them. I thought, i was missing something but looks like firefox is missing it.

Jm
September 01, 2008

# re: FireFox 3 and Static File Caching Problems

When develop in WC and Firefox, I need to press CTRL+F5 to force Firefox reload all. but If in your headers add no-cache control this don't occurs a lot of time.

Rick Strahl
September 01, 2008

# re: FireFox 3 and Static File Caching Problems

@JM - sure, but that only works if you are generating the output on the server. if you're serving static files that's not appropriate because you want the static content to cache yet still be responsive to the static file changing.

max-age
September 01, 2008

# re: FireFox 3 and Static File Caching Problems

You are aware that your server sends the stylesheet file with a Cache-Control: max-age=86400 header, meaning that the resource may be cached for up to 24 hours without revalidating, right? This behavior is, as far as I can tell, compliant with the HTTP standard.

My version of Firefox 2 does not send a request for resources which are still valid in the cache. (But it does send a request when pressing reload; this might have changed in FF 3, I don't know, and I can't check right now.)

Of course, this means you'll have to change the resource's URL if you want to force clients to get the new version. Alternatively, you could modify the caching directives sent by your server so that clients are always required to revalidate (Cache-Control: must-revalidate, see the HTTP spec for details).

Rick Strahl
September 01, 2008

# re: FireFox 3 and Static File Caching Problems

Yes I can live with the fact that FF will not check for 304's on every hit. That's probably not a bad idea. However, a full Refresh should force all resources to be retrieved from the server either by retrieving or checking for last-modified.

It doesn't work properly at least not in the frames page. All other browsers I checked: IE, Opera, Safari, properly check all links on the server including in child frames. Firefox does not.

Firefox also doesn't refresh regular pages on a regular Refresh - it requires Shift-Refresh which is totally bogus. An average user might figure out that his page is not properly loaded and hit refresh to attempt to get it refreshed properly. But hitting Shift-Click is not something that the average user will think of. Heck I still can't keep Shift-Refresh and Ctrl-Refresh and clicks straight.

The Refresh behavior is what's broken IMHO and what is the main cause for the problems I and others describe.

jotabede
September 01, 2008

# re: FireFox 3 and Static File Caching Problems

Maybe changing "browser.cache.check_doc_frequency", in about:config, from 3 to 1 will fix this. Details here: http://is.gd/26BX I've not tested it yet.

Atanas Korchev
September 01, 2008

# re: FireFox 3 and Static File Caching Problems

Hitting Refresh (F5) seems to trigger 304 requests in FF3 (tested on this very page). However if I just hit enter in the address bar to load the same URL no 304 is ever generated. The same thing occurs in IE7 though (tested with Fiddler) - F5 caused 304 whilst simply loading the URL does not. What gives?

Steve from Pleasant Hill
September 01, 2008

# re: FireFox 3 and Static File Caching Problems

On one site I fiddle with, which does have a couple of frames, when the CSS is updated I must right-click the frame and select 'Reload this Frame' to pick it up, in FF2.

Rick Strahl
September 01, 2008

# re: FireFox 3 and Static File Caching Problems

@Atnas - that would be the behavior I'd expect. Have you mucked with the default cache settings though?

I don't see this behavior (304s being sent on a plain refresh). Basically Refresh appears to be resubmitting the page EXACTLY as it was sent by the last request. So if the last request was a Shift-Refresh to force a full refresh then hitting just the Refresh button does the same again also generating the 304s. But if you just hit the page again from a link or typing in the address bar it will do exactly the same and NOT hit 304s. At least that's what I'm seeing in my setup here.

As I said in the post - I'd expect Refresh to be more agressive in reloading content. That's part of the purpose of Refresh button is to ensure all resources are reloaded.

While I think you can change the behavior via about:config settings, that's not something you'd want to force on your site users.

Yordan Georgiev
September 01, 2008

# re: FireFox 3 and Static File Caching Problems

Well , may be Google will do it right than ....
http://www.scottmccloud.com/googlechrome/

Mark Gibaud
September 02, 2008

# re: FireFox 3 and Static File Caching Problems

This plugin may help alleviate the problem in terms of developing with FF3:

http://clearcachebutton.mozdev.org/

Tom
September 02, 2008

# re: FireFox 3 and Static File Caching Problems

You don't need to add the querystring to the url for the css file, just rename of the file... Whack a "2" on the end or something, since you're rewriting the html too anyway.

Nicholas
September 03, 2008

# re: FireFox 3 and Static File Caching Problems

Yordan,

Google Chrome is correctly sending 304 requests, like FF3 should be.

Steve
September 03, 2008

# re: FireFox 3 and Static File Caching Problems

Yeah FF is a pain in the arse where caching is concerned. I just removed our old archery site which was a frames based static html system and replaced it with a dynamically generated asp .NET version. (same directory and same url). People who are using FireFox are still seeing the old version unless they do a ctrl-f5. This, even after they close their browser and re-open. Tested in IE, Safari and Chrome and no problem.

The thing is an average user won't even know that they're seeing old stuff. I've been investigating what I could have done to have prevented this and I can't find a solution. So, not only are they seeing the old site, but I can't even find a way to inform them (the general public user) that they're seeing the old site.

I also have no access to the IIS of the server that the website resides on so if there is a solution by doing someting in IIS it is of no use to me.

I personally don't use Firefox because I can never be certain I'm seeing up-to-date web pages.

Ben Amada
September 03, 2008

# re: FireFox 3 and Static File Caching Problems

Like others, I try to avoid browsers not picking up updated CSS/JS files by adding a querystring value.

I have it pretty automated now where I insert the CSS file's timestamp in the .NET Cache. I add a cache dependency for this item -- where the dependency is the actual CSS file. When I update the file, the cached timestamp is automatically removed from cache and the new timestamp is added into cache on the next request. What's obviously nice about this is that I don't have to manually modify the querystring. An example CSS file name with querystring in the served HTML looks like:

styles.css?v=20080817152536

similar
September 04, 2008

# re: FireFox 3 and Static File Caching Problems

Ben, I do something similar with caching in .net. I have a class that modifies the filename being output with the timestamp, like so: filename.25642352345.css. I also set a far future expires header on the files. I then map that back to the actual file when requested.

Boris
September 04, 2008

# re: FireFox 3 and Static File Caching Problems

Note that if you're sending Last-Modified but not Expires, then the UA is supposed to calculate an expiration date based on the Last-Modified date (see the HTTP RFC). The expiration date is the earliest point at which the UA will make the If-Modified-Since response to revalidate the cache. The longer in the past Last-Modified is, the further in the future the computed Expires will be (again, see the HTTP RFC).

That's my best guess as to what you're hitting, though I don't think this behavior has changed from Firefox 2 to Firefox 3. But note that if you're not using the former much and it didn't have the files with the ancient Last-Modified date cached... you wouldn't hit the problem.

The issues with reload sound like a bug for sure. Any chance of getting that filed, and ideally a page that reliably shows the problem?

Boris
September 04, 2008

# re: FireFox 3 and Static File Caching Problems

Oh, and the upshot is that if you want to be able to propagate content out in no more than X minutes then you need to always send an Expires header for no more than X minutes into the future.

JM
September 06, 2008

# re: FireFox 3 and Static File Caching Problems

@Rick I think you can add a custom header from iis to your CSS files to set a expiration date to force FF to reload files, I can't remember right now how do that, but I am reviewing :)

BB
September 17, 2008

# re: FireFox 3 and Static File Caching Problems

I think there is a little misunderstanding of the protocol here. A browser doesn't send a "304 request." That is a server response code. That happens when a user agent (read browser) makes a request for a resource. The request headers will include If-Modified-Since and possibly ETag headers. The server will determine from those two headers if the file has been updated. If it has not it sends a 304 response code.

The problem you're seeing is from previous requests of the resource. If there was a Cache-Control header that specified the max age of the file or an Expires header specifically saying when the resource becomes stale, the server told the browsers "Don't worry about requesting this resource before this time." The browsers are doing the correct thing here in not making the request. Essentially there's nothing you can do to force them to reload if they don't want to. Your safest bet is to rename the resource to force the browser to load it and in the future set up your server to only cache files for a shot period of time.

Rick Strahl
September 17, 2008

# re: FireFox 3 and Static File Caching Problems

@BB - I agree that the behavior of the 'regular' requests not asking to get the latest resources is not a big problem - that's what caching is supposed to accomplish of course. The big issue is that in many scenarios FireFox doesn't refresh even on a full forced Browser Refresh operation and that is a problem.

As I mentioned I have a frames based setup that I was unable to get refreshed AT ALL other than forcing a URL change. I've now changed the expiration to a smaller number and that works, but FF doesn't refresh the associated static resources under any manually applied browser action.

Doug
September 17, 2008

# re: FireFox 3 and Static File Caching Problems

You have written all that code for your Script Managers that write JS links, why not just extend it to write CSS links as well - then you can have your code append the "?i=1" based on version number or something....?

Rick Strahl
September 17, 2008

# re: FireFox 3 and Static File Caching Problems

@Doug - Because it's static content (often from static pages). For now the problem is solved by having a shorter Expires header so that at least every few hours FF is required to recheck.

BB
September 18, 2008

# re: FireFox 3 and Static File Caching Problems

For things stuck in your cache during development Firefox gives you access to manually clear your cache. Go to Tools->Clear Private Data (FF3). You're presented with a list things you can clear, including the cache.

Also, if you really want to verify what is being cached have a look at about:cache. You'll get links to both the memory and disk caches. Looking at those you'll see what the browser has cached and when it thinks the content expires.

Obviously this isn't something for your users (your header changes fixed that) but from a development standpoint it's a life saver. If you do it often look for the Clear Cache Button add-on. I have it sitting next to my address bar and can clear my cache with one click.

Patrick Miller
September 25, 2008

# re: FireFox 3 and Static File Caching Problems

This has been driving me crazy, and I can't believe the FF developers don't go crazy too! How can they work? I'm a web developer and I change CSS files constantly just to see what might look better. Never a problem in FF2, but now... So far the best solution for me is this one from Ben:

I have it pretty automated now where I insert the CSS file's timestamp in the .NET Cache. I add a cache dependency for this item -- where the dependency is the actual CSS file. When I update the file, the cached timestamp is automatically removed from cache and the new timestamp is added into cache on the next request. What's obviously nice about this is that I don't have to manually modify the query string. An example CSS file name with query string in the served HTML looks like: styles.css?v=20080817152536

Reagan
October 14, 2008

# re: FireFox 3 and Static File Caching Problems

I have a situation where I go to a third party site to download a recently recorded phone call for a client. I save the file with the users session id for the file name. When they go to listen to another call using firefox, it always only loads the first call they listened to. No problem whatsoever with I.E. It's annoying to hear that there's probably not going to be a solution for this.

G
November 17, 2008

# re: FireFox 3 and Static File Caching Problems

To add to the frames-confusion, i suspect might that firefox3 sometimes reloads a frame twice, if you use the classical: parent.frame2.location.href = 'newpage.asp'.
Would be interesting to hear anyone verify this, since it only happens in firefox3. Is this a known problem?

Mat Gessel
November 20, 2008

# re: FireFox 3 and Static File Caching Problems

Here is what I use to force/prevent caching. Works everywhere except for caching 1MB+ files in Safari/WebKit.

if (forceDontCache)
{
    setHeader("Cache-Control", "no-cache no-store must-revalidate");
    setHeader("Pragma", "no-cache"); // HTTP/1.0
    setDateHeader("Expires", 86400000); // January 2, 1970
}
else if (forceCache)
{
    // the w3c spec requires a maximum age of 1 year
    // Firefox 3+ needs 'public' to cache this resource when received via SSL
    setHeader("Cache-Control", "public max-age=31536000");
    
    // necessary to overwrite "Pragma: no-cache" header
    setHeader("Pragma", "");

    // this prevents the browser from requesting the resource for 1 year
    setDateHeader("Expires", currentTimeInMilliseconds + 31536000000l);
}

Alex Epshteyn
December 08, 2008

# re: FireFox 3 and Static File Caching Problems

Matt, your Java code doesn't fix this problem in Firefox (I just tried it). The issue is that FF completely ignores all of these headers and always caches URLs of the resources embedded in the page, such as iframe src values.

Has anyone filed a bug for this with Firefox yet? If not, how can we all be so lazy? :)

Alex Epshteyn
December 08, 2008

# re: FireFox 3 and Static File Caching Problems

Okay looks like a truly selfless person did take the time to file a bug report :)

https://bugzilla.mozilla.org/show_bug.cgi?id=441751

And furthermore, it's just been fixed on trunk! The problem is we still have to support the FF versions that came and will come before this makes it into a release...

James
December 17, 2008

# re: FireFox 3 and Static File Caching Problems

Hey,

I spent a few hours going crazy with the same problem. I found that if I disabled the 'Firebug' extension in FF3, it would request 304's again.

Darla
January 07, 2009

# re: FireFox 3 and Static File Caching Problems

I got the caching solved on page back by putting all three in the load event.

Response.Cache.SetCacheability(HttpCacheability.NoCache)
Response.Cache.SetAllowResponseInBrowserHistory(False)
Response.Cache.SetNoStore()

When I page back now my original page is loaded. It didn't work in FireFox until I added the Response.Cache.SetNoStore()

Hope this may help you.

Bob
January 08, 2009

# re: FireFox 3 and Static File Caching Problems

James - You are dead on. I was scratching my head on this problem for 2 hours until I found this post & your suggestion to disable Firebug in FF 3.

Anyone know why Firebug is prohibiting the 304's?

Anna Kolesnik
January 20, 2009

# re: FireFox 3 and Static File Caching Problems

Hello mates ..
I have just found a solution on tech blog: [http://blogs.helion-prime.com/]

have a nice day

garvek
February 17, 2009

# re: FireFox 3 and Static File Caching Problems

I confirm that FF3 is still very messy with cache and frames.
It is even worse if your pages are big or when you have extensions like Firebug.
On my webapp I have double request (checked on Apache logs) and even strange renders like the 2 results being merged (I have made a page which doesn't display the same thing every time, and the 2 outputs are melt together O_o, like 2 thread trying to write at same time).

At the moment my only fix is to use Firefox 2, ... or Opera.

Norm
March 27, 2009

# re: FireFox 3 and Static File Caching Problems

I ran into this problem the other day. My personal homepage which was built ages ago never changes, but even better, the Wx Underground site does the same. I'm sure there are more pages that don't update. I see no new posts in the last month or so. Is everyone fixed?

Fran
April 10, 2009

# re: FireFox 3 and Static File Caching Problems

I use FF 3.07 with Firebug 1.3.3 and during designing a web page stored locally (accessed as a file not through a web server) I was experiencing the same issue with the refresh button loading the old cached version of the page. Very annoying!

However I found that changing the following setting solved the problem (confirming jotabede's idea):

browser.cache.check_doc_frequency = 1

1 = Check for a new version every time a page is loaded
3 (default) = Check for a new version when the page is out of date

See: http://kb.mozillazine.org/Browser.cache.check_doc_frequency

Fran
April 10, 2009

# re: FireFox 3 and Static File Caching Problems

I agree though that the default refresh behaviour of FF should be changed to what one expects, ie certainly ignoring the cache when shift-clicking refresh. Also the chaching options should be shown in the UI, not exclusively accessible from about:config.

Issac
June 14, 2009

# re: FireFox 3 and Static File Caching Problems

I have encountered this problem and solved it by specifying an Expires header set to the past (together with the last-modified).
This way although a last-modified is passed to the browser, the expires header forces the ff to create a 304 request each time.

Mike
July 01, 2009

# re: FireFox 3 and Static File Caching Problems

Improper caching is definitely a problem in FF3 (maybe previous versions as well). I have re-worked a client's site, including adding precise, explicit cache-control headers, as well as others. I purposely removed the "Expired" headers on all files that Apache was adding so that I have complete control over all caching.

This technique works great in IE 7 and 8, Google Chrome and Opera. In these browsers, when a link is clicked anywhere in the site, I get re-validation, as I should. BTW, for those that say the browser should send a "304" header, the "304" is a *response* header that the server sends to the browser, not a request header.

In FF3, when the links are clicked, I get no re-validation. When a standard refresh is initiated in FF3, *sometimes* FF will re-validate, but most times it won't. When I do a shift-refresh, FF sends the correct headers and performs a complete reload of the page.

This is not per HTTP specs, and should be fixed. I do not like IE, and never have, and would really like to see FF become more prevalent. If they don't fix their validation model, this will not happen.

Here are the headers that I am sending to the browser on most pages:
Cache-Control: public, must-revalidate, max-age=90000, post-check=60, pre-check=60, proxy-revalidate, no-transform

Thes headers should cache the page for 25 hours, but always check to see if the content has changed. As I mentioned, this works in all browsers I've tested except for FF. FF totally ignores these headers. I have also tried many different variations, inccluding changing the values of max-age, post-check, pre-check, etc.

Mike
July 01, 2009

# re: FireFox 3 and Static File Caching Problems

Forgot to mention, I am also creating "ETag" headers for each file using inode-date-size. This also does not affect FF's silliness.

Mike
July 01, 2009

# re: FireFox 3 and Static File Caching Problems

One more note: I tried setting the browser.cache.check_doc_frequency to a value of 1, and this forces FF3 to respect the caching directives that I send it from the website. In other words, it behaves like other browsers. That is, unless the "refresh" button is pressed more than once for a given resource.

The problem with this is that every person that visits a site more than once must make configuration changes to their browser in order to view the site as it was (mostly) intended. Not a solution.

The only other solution that I can think of is to send no-cahe, no-store and past expires headers to all FF users, requiring browser sniffing, etc. Again, not a solution.

Maybe Mozilla could just fix their browser.

Jeff
August 27, 2009

# re: FireFox 3 and Static File Caching Problems

I'm having the opposite problem! If I send the browser this header (validated via HttpFox):

Cache-Control: private, max-age=86400

...and then click refresh, it still goes to the server with if-modified-since. I'm trying to prevent all the if-modified-since checks that tax the server and slow down the page load.

It works if the server is my local machine, but not if it's the ISP server.

Any ideas?

dave
December 18, 2009

# I dont know if this is relevant

I found FF3 would not respond (by always refreshing) to the usual "no-store" etc headers when browsing to a website hosted on the same machine (ie all local on my laptop)

When I went to another laptop and browsed to the original laptop's website, FF3 auto-refreshed the page as expected. Maybe some http headers are ignored when locally browsing?

( still, at least i dont use asp.net webforms anymore ... hit 'BACK' in that environment and its a car-crash eh?)

Ramana
May 20, 2010

# re: FireFox 3 and Static File Caching Problems

I had a similar problem using struts where the back button does not hit the rendering action class for FF as it takes the data from the cache to populate the form but works fine for IE.
So i set the following headers in cache as follows and it works for me.
response.setHeader("Cache-Control", "no-cache,no-store");
response.setHeader("Pragma", "no-cache");
response.setDateHeader("Expires", -1);
 

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