This script makes the background of a thumbnail yellow (the kind of yellow you get when you click the quick-menu on the left of your nickname) so you can see when you are hovering a thumbnail. Also, it creates a background of the same colour at some buttons in your profile page, such as the "Browse Gallery", "Browse Favourites" and "Show all Friends" buttons, which also don't have (by default) any hovering status.

It might be disturbing for some, but I like it nevertheless, because I want to know what I am hovering. You can easily change the colour of hover, and you can add other effects (such as border, underlining, changing colour etc), by writing in simple CSS. If you need any help, ask me :D :D