If you are running the latest version of Safari, version 4, you have probably noticed the new TOP Sites Window. Essentially, it's your most visited sites according to Safari. However, you can edit it and make sure some sites always stay on top. Safari 4 is required for this tip.
1. Launch Safari 4
2. Click on the Top Sites icon, if the page isn't already up.
3. Click on 'Edit'
4. Notice that the website gallery now shows each site with an X or a Push pin. To Remove a site, click the 'X' and another Top site will move up into it's place.
If you want to make sure one of these sites stays in the top list, click on the Push Pin and that will keep it from being replaced.
You'll notice the icon will change to a blue color and now looks like it's been pushed into a piece of corkboard.
5. Now, click on DONE.