This would cause a problem if, say, you're using the NiceTitles hack to get pretty tooltips, then want to install the Uber Blockquotes hack to make your citations and links appear below your blockquotes...both use window.onload.
(I wrote up a nice article on my site yesterday, but the servers have been down since 8:00pm last night. I guess their sysadmins all got the holiday off...)
// Function to allow multiple onload functions to be called
window.onload = multipleOnload;
// end function
Just put any functions you want to call inside multipleOnload and you're set!