Kind of unrelated; But maybe someone knows.

David J. david at
Thu Dec 23 03:58:48 MSK 2010

Thanks mike;

Would you happen to have any articles or information that goes deeper 
into that?

I understand the concept clearly; Obviously on CSS or JS files are any 
versioned content; You wouldnt want that data cached;

But  I never saw the technique mentioned before; So I would like to 
learn a bit more about it.

Thanks Again.

On 12/22/10 7:49 PM, Michael Shadle wrote:
> On Wed, Dec 22, 2010 at 4:43 PM, David J.<david at>  wrote:
>> I was wondering why some sites have
>> <script src="path/to/javascript.js?432532432"></script>
>> What is the "?432532432" or whatever used for? Is it a versioning thing.
>> I see it on many of the bigger sites.
>> <link href="/css/layout.css?1291917579" media="all" rel="stylesheet">
>> Thanks for any info.
> Forces the user's browser to treat the same on the server as a
> different one. Or, a lot of the time, CDNs - a technique known as
> "cache busting"
> It will force a browser and most CDNs to re-cache the file as a fresh
> copy as it includes the query string as part of the key. Otherwise due
> to Expires headers, CDNs and other caching behavior, clients wouldn't
> know that a new copy of a specific file might be fresh.
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