Serve diffrent CSS and JavaScript files with htaccess

Question

Would it be a bad idea to use RewriteRule in .htaccess to serve different CSS and Javascript to browsers that doesn't support CSS3? If so why?

For example I would like to serve special CSS and Javascript to browsers that doesn't support CSS3 fully.

I am aware of that you can use <!--[if xx]> in HTML but I tought that doing it on server level would be cleaner.

Please guide me.

Example of how I was planning to do it:

RewriteEngine On
RewriteCond %{HTTP_USER_AGENT} "MSIE 9" [or]
RewriteCond %{HTTP_USER_AGENT} "MSIE 8" [or]
RewriteCond %{HTTP_USER_AGENT} "MSIE 7" [or]
RewriteCond %{HTTP_USER_AGENT} "MSIE 6"
RewriteRule the-file-for-all-other-browsers.css /css/style-for-ie-browsers-below-10.css [NC,L]

Surely detecting the brower using PHP and serving different files in a switch statement would make more sense? — ChrisW
– ChrisW, Commented Jun 1, 2012 at 14:31
You cannot know the browser's capabilities on the server side, and user agent sniffing is not a recommended practice. — lanzz
– lanzz, Commented Jun 1, 2012 at 14:31
ChrisW: Not in my case. lanzz: By using RewriteCond %{HTTP_USER_AGENT} I can detect browsers in the same way as using <!--[if xx]> — user1087110
– user1087110, Commented Jun 1, 2012 at 14:36
Interesting approach, but you haven't answered why you can't use either CSS3PIE, or use PHP to detect the browser (or, why you can't use progressive enhancement instead) — ChrisW
– ChrisW, Commented Jun 1, 2012 at 15:55
Shorly I could build my site in PHP but I prefere working with static HTML files (in the end, thats what will be served to the browser any way). CSS3PIE wont work for the things I am working on. Using javascript might be a better option than using htaccess! Maybe Google would find it better. — user1087110
– user1087110, Commented Jun 1, 2012 at 19:59

Dunhamzzz · Accepted Answer · 2012-06-01 14:33:05Z

2

How did you plan on doing this with .htaccess? Sniffing the user-agent string can lead to false positives and generally isn't recommended. You should throw on something like Modernizr, You can then prepare graceful degradations/plugins for the wide range of browsers that don't support a certain features you're looking for.

Also worth mentioning It's minimal over-head to use the  tags, as other browsers will ignore them and not load the content, they will also not trigger on browsers that use similar user agent strings (points to Opera).

answered Jun 1, 2012 at 14:33

Dunhamzzz

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user1087110 Over a year ago

Thanks Dunhamzzz. I was planing to use RewriteCond %{HTTP_USER_AGENT} and RewriteRule to serve the old browsers other files (bigger files with lots of fixes using images). Some how I must correct old browsers to be able to use CSS3 the way I want :S

Tango Bravo · Accepted Answer · 2012-06-01 14:33:26Z

1

I'd say it's a bad idea. That .htaccess rewrite will get processed on EVERY request. That means for images, every file, everything. That is a lot of overhead and can lead to slowing down the site.

answered Jun 1, 2012 at 14:33

Tango Bravo

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user1087110 Over a year ago

Thanks. Thats a good point. One reason for using javascript instead.

Diodeus - James MacFarlane · Accepted Answer · 2012-06-01 14:29:28Z

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Consider using CSS3PIE, it provides polyfills for IE 9,8 and 7 to give them CSS3 features.

answered Jun 1, 2012 at 14:29

Diodeus - James MacFarlane

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Comments

Ortiga · Accepted Answer · 2012-06-01 14:32:59Z

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I think it's bad, because you can't determine functionality support in htacess.

You shouldn't be using browser sniffing to provide graceful degradation, but rather identify if the browser support the required functionalities before showing them the advanced features (progressive enhancement)

answered Jun 1, 2012 at 14:32

Ortiga

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