So it’s Command + D that makes a bookmark in Safari for that site you want to find again sometime! With Mountain Lion not showing that little + sign next to the URL in the bar it wasn’t obvious how bookmarks work now.
Take a look here: http://www.apple.com/safari/features.html gives brief info on the 250+ features of Safari. So, to find that same page again? You can bookmark it, and you can change the wording of that bookmark. Click on the illustration to enlarge it, then click to return to this place.
Here's how I renamed it for my own use.