Changing css - can't se changes or changes in firebug?

Hey.

I mad a change til at css file called uc_catalog.css, that comes with ubercart module.
The only thing i added is 'background: white;' and that also work when i put it in to firebug.

But when i implement it to the original css file, i can't se the changes i made when i go to firebug.

I tried to clear all the caches, also in my database.