hmm then no need to use this att all....

is it working at winodws servers?

is step 3 bakwards?

I had .css in there, not .php

Good work..

But is there any increase in performance?

Increase preformace would be removing gzip, decreasing preformance would be adding it back.

This code
$cssfilename = 'clientscript/vbulletin_css/style-' . substr(md5(microtime()), 8, 8) . '-' . str_pad($styleid, 5, '0', STR_PAD_LEFT) . '.css';
is in file alreadey
and iam not editing it before

This is pointless since browsers cache all css and javascript when they are seperate files. It IS why you should always have them in a seperate file. Most webservers are running mod_deflate or equivilents that compress text in a way that browser can interpret. Browsers check and compare the time and date of last update for css and javascript files before downloading. So unless you have changed the css file, they will not be downloading the css in the first place.

But, do as you please.

Personally, I think gzipping css files will not add as much bandwidth savings as gzipping .php files would but more bandwidth savings and faster initial page loads make doing something like this worth it.