Fun "bug" a co-worker of mine discovered a few months ago.
Send Safari 3.1 the following code while watching its requests to your server.
<div id='test'>content</div>
#test { background: url( 'test.png' ); }
#test { background: url( 'test2.png'); }
Safari will try and download both test.png and test2.png, while all other browsers only make the request for test2.png.