Comments on: Two Important Differences between Firefox and IE Caching http://blog.httpwatch.com/2008/10/15/two-important-differences-between-firefox-and-ie-caching/ News, articles and all things HttpWatch Wed, 07 Jan 2009 14:37:42 +0000 http://wordpress.org/?v=2.6.3 By: yannack http://blog.httpwatch.com/2008/10/15/two-important-differences-between-firefox-and-ie-caching/#comment-3039 yannack Thu, 18 Dec 2008 10:14:25 +0000 http://blog.httpwatch.com/?p=177#comment-3039 Thanks for your answer. That is what I suspected, sadly :( I knew about the varying URL trick, but this is not a valid option for me, for two reasons: - I do not have control over most images, and some refuse to show if a parameter is added to the URL - I don't want FF to reload cached images which are still valid. Many images never change, in fact, it is the case most of the time. I don't want to add useless traffic, I just want expired images to reload. I guess it's just "too bad for me" :( Thanks again for your answer though! Yannack Thanks for your answer. That is what I suspected, sadly :( I knew about the varying URL trick, but this is not a valid option for me, for two reasons:
- I do not have control over most images, and some refuse to show if a parameter is added to the URL
- I don’t want FF to reload cached images which are still valid. Many images never change, in fact, it is the case most of the time. I don’t want to add useless traffic, I just want expired images to reload.
I guess it’s just “too bad for me” :(
Thanks again for your answer though!
Yannack

]]> By: Httpwatch Blog http://blog.httpwatch.com/2008/10/15/two-important-differences-between-firefox-and-ie-caching/#comment-3036 Httpwatch Blog Thu, 18 Dec 2008 09:41:15 +0000 http://blog.httpwatch.com/?p=177#comment-3036 yannack, You cannot prevent caching in Firefox. Using no-store does force the use of the in-memory cache, but it only affects the reload of pages - not embedded resources such as images. The only way we know to force an image reload in Firefox is to use a varying query string on the URL. We used a random number on the end of the image URL in this sample: http://www.httpwatch.com/httpgallery/headers/ yannack,

You cannot prevent caching in Firefox. Using no-store does force the use of the in-memory cache, but it only affects the reload of pages - not embedded resources such as images.

The only way we know to force an image reload in Firefox is to use a varying query string on the URL. We used a random number on the end of the image URL in this sample:

http://www.httpwatch.com/httpgallery/headers/

]]> By: yannack http://blog.httpwatch.com/2008/10/15/two-important-differences-between-firefox-and-ie-caching/#comment-3004 yannack Wed, 17 Dec 2008 18:27:11 +0000 http://blog.httpwatch.com/?p=177#comment-3004 Hi, i am working with some caching issues. I have some javascript code which loads images from various websites, and refreshes these images, by simply clearing the source of the img or by changing the background of the iframe, depending on the type of display. However, I have found that in many cases, Firefox doesn't reload the image from source but uses the cached version; and this despite the fact that there is a Expires, last Modified, and Cache-control:max-age set so as to have an expiration after one second. Internet Explorer does not have this problem. I wonder if you, as experts of this domain, might know why, and how to prevent this apparently abnormal behavior? Thanks a lot! Here is a sample html page which doesn't reload properly with firefox, but does with IE: function clearbg(){ document.getElementById("myframe").style.background="none"; document.getElementById("mypic").src=""; setTimeout("setbg()",1000); } function setbg(){ document.getElementById("myframe").style.background="url('http://www.sytadin.equipement.gouv.fr/tempsreel/parisint.gif')"; document.getElementById("mypic").src="http://www.sytadin.equipement.gouv.fr/tempsreel/parisint.gif"; setTimeout("clearbg()",1000); } Hi,
i am working with some caching issues. I have some javascript code which loads images from various websites, and refreshes these images, by simply clearing the source of the img or by changing the background of the iframe, depending on the type of display. However, I have found that in many cases, Firefox doesn’t reload the image from source but uses the cached version; and this despite the fact that there is a Expires, last Modified, and Cache-control:max-age set so as to have an expiration after one second. Internet Explorer does not have this problem.
I wonder if you, as experts of this domain, might know why, and how to prevent this apparently abnormal behavior?
Thanks a lot!

Here is a sample html page which doesn’t reload properly with firefox, but does with IE:

function clearbg(){
document.getElementById(”myframe”).style.background=”none”;
document.getElementById(”mypic”).src=”";
setTimeout(”setbg()”,1000);

}

function setbg(){
document.getElementById(”myframe”).style.background=”url(’http://www.sytadin.equipement.gouv.fr/tempsreel/parisint.gif’)”;
document.getElementById(”mypic”).src=”http://www.sytadin.equipement.gouv.fr/tempsreel/parisint.gif”;
setTimeout(”clearbg()”,1000);
}

]]> By: Httpwatch Blog http://blog.httpwatch.com/2008/10/15/two-important-differences-between-firefox-and-ie-caching/#comment-2786 Httpwatch Blog Tue, 09 Dec 2008 15:26:31 +0000 http://blog.httpwatch.com/?p=177#comment-2786 Pascal, That bug appears to be related to using the back button to visit a page that was the direct result of a POST. That's a not a good idea as it breaks the back button: http://blog.httpwatch.com/2007/10/03/60-of-web-users-can%e2%80%99t-be-wrong-%e2%80%93-don%e2%80%99t-break-the-back-button/ It you always redirect a POST to a GET then the no-store cache directive fixes the problem. Pascal,

That bug appears to be related to using the back button to visit a page that was the direct result of a POST.

That’s a not a good idea as it breaks the back button:

http://blog.httpwatch.com/2007/10/03/60-of-web-users-can%e2%80%99t-be-wrong-%e2%80%93-don%e2%80%99t-break-the-back-button/

It you always redirect a POST to a GET then the no-store cache directive fixes the problem.

]]> By: Pascal http://blog.httpwatch.com/2008/10/15/two-important-differences-between-firefox-and-ie-caching/#comment-2782 Pascal Tue, 09 Dec 2008 14:08:05 +0000 http://blog.httpwatch.com/?p=177#comment-2782 "Also, if the page is reached using the Back button there’s no round-trip to the server and Firefox simple re-loads the page directly from the cache." It's a bug of Firefox 3. https://bugzilla.mozilla.org/show_bug.cgi?id=441751 “Also, if the page is reached using the Back button there’s no round-trip to the server and Firefox simple re-loads the page directly from the cache.”

It’s a bug of Firefox 3.
https://bugzilla.mozilla.org/show_bug.cgi?id=441751

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