Safari keeps opening your last visited pages after upgrading to Lion

Well, the case is that setting Homepage to “about:blank” is not enough. You have to change global applications’ preferences.

Go to System Preferences, General and uncheck the box with description “Restore windows when quitting and re-opening apps”.

BTW, I think I know why this feature is enabled. Safari 5 crashes so often, that after crash, you don’t have to, at least open pages after it has restarted.