Click on a site thumbnail to visit that site. This will always work.
You can also middle click and right click the thumbnails. They work like normal links.
Type Enter to visit the first site on your list.
You can type the number 1 to visit the first site. 2 visits the second site. 3 visits the third site, and so on.
Typing 0 opens the 10th site on your list. You can also type Shift+1 to visit the 11th site. Shift+2 visits the 12th site, and so on.