Go ahead, customize the Web to better suit your needs!
Countless books have been written explaining how to customize various operating systems and applications. But what about Web sites, like Google, eBay, or Yahoo!?
Now with Mozilla/Firefox, you can (ok, up to a certain point). You do this by editing the userContent.css file (look for it in your profile directory) and writing CSS that gets applied to Web pages as you browse. For instance, I think the text area in Yahoo! Notepad text area is way too small. Hey, we have 19" and 21" monitors nowadays! Make it bigger by adding this to your userContent.css:
/* Yahoo! Notepad: make textfield bigger */
And of course, you can use that same file to block advertisements on Web page altogether.