One thing that annoys me about Safari is that it stores internet site's favicons. These files quickly add up to MBs of space. That's bad if you use Apple's Backup software to up backup Safari to your iDisk. But there's a quick-fix. Go to Users -> username -> Library -> Safari.
Go into the Icons folder and delete everything in there. Once you have deleted everything, return to the Safari folder and click on (highlighting) the Icons folder. Get Info and click the triangle next to Ownership & Permissions. Change the Owner to you (your short Unix name) and set the access to "Read only" then set the rest of the access lines to "No access"
Now when you surf the net, you'll find that Safari displays the icons, but when you quit and restart Safari all of those icons are gone. Your iDisk will love you in the morning!
Mac OS X Hints
http://hints.macworld.com/article.php?story=20030703013750909