Hi - type in a letter and your search box will say click to go to "letter" authors where "letter" equals whatever letter you want. I think it only works when you have an author of that specific letter.
A sort of shortcut is you can navigate to a specific page. So say you have 20 pages and you want to get somewhere in the middle you an type in 10 (alt Q and alt P) and just click to go to that page.
Hope that helps you
