Since the release of Safari 4, Apple has used Top Sites as the default page whenever a Mac user opens the Web browser. While this feature is designed to make it easier to get to the websites you visit most often, not everyone will find it useful. Disabling Top Sites takes just a few clicks of the mouse. You can disable specific websites from being displayed in Top Sites, as well as remove this feature entirely.
Launch Safari. By default, the Top Sites screen is displayed. Hover the cursor over any website thumbnail you never want to be shown. Click the "X" that appears in the corner to delete it from Top sites.
Click the "Safari" menu and choose "Preferences."
Click the "General" tab, then click the "New Windows Open With" menu and change it from "Top Sites" to any other option, like "Home Page" or "Empty Page." This will stop Safari from displaying your top sites when you launch the browser or open a new tab.