Behind the scenes, Safari keeps track of the Web sites you've visited in the last week or so, neatly organized into subfolders like Earlier Today and Yesterday. It's a great feature when you can't recall the URL for a Web site that you visited recently—or when you remember that it had a long, complicated address and you get the psychiatric condition known as iPod Touch Keyboard Dread.
To see the list of recent sites, tap the button, and then tap the History folder, whose icon bears a little clock to make sure you know that it's special. Once the History list appears, just tap a bookmark (or a folder name and then a bookmark) to revisit that Web page.
Some people find it creepy that Safari maintains a complete list of every Web site they've seen recently, right there in plain view of any family member or co-worker who wanders by. They'd just as soon their wife/husband/boss/parent/kid not know what Web sites they've been visiting.
You can't delete just one particularly incriminating History listing. You can, however, delete the entire History ...