HttpCombiner is a HttpHandler allows you to gather all css and js files together which decreases amount of http requests made to server when user requests a page and also to cache the generated files, which makes you websites to load faster. You can download http handler from Microsoft’s website by clicking here and you can read Omar’s article on how to implement the handler here. Original handler written by Omar Al Zabir.
It took me few minutes to configure the handler to work, it is easy to use and well documented. So i advice you to read Omar’s post before continuing with modifications.