I use the Firefox landing page shortcuts for sites I visit often. This list seems to be prioritized according to sites I enter with the address bar. The more I enter it, the higher it is on the list and specifically doesn't get removed.
If I only enter that site by clicking the icon on the start/landing page, it eventually goes down in the listing and eventually disappears, forcing me to enter using the address bar to get it back.
Clicking one of these links should be counted the same as me entering the address in the address bar.