I can here the cries already, “You don’t **design URL’s**, they’re just identifiers.” Well, you’re wrong, they are not just identifiers, they are a part of your UI, they can increase or decrease your CTR. They are a major tool in your SEO arsenal.
A fast website equals a good user experience. It also pleases search engine spiders. Using a little PHP you can combine & minify all of your CSS files on-the-fly. This not only reduces the overall filesize, but also minimises HTTP requests.