What is the promote button and can it be used for anything?

[racemepls]

When you do a Google search and when the results come up, next to the cache button there are three grey buttons. The middle one is a up arrow button that says promote. I was wondering what that is.

 

[djbaxter]

That's a feature of Google's personalized search. You click the "promote" arrow to have that site come up first (or in the first X result) in subsequent searches by you for that search term. It doesn't affect actual Google ranking for other searchers, although if enough people do it it potentially could.