using + and - keys to rate picture

[xobix]

this would assume a good/notgood sort of rating, but that would be ok for me. Doesn't seem too hard to do.
Goal would be to see what is liked/not liked instead of, yeah, i like this one a little, this one a lot.. 
I find it too much of a hassle to use the mouse to rate a picture, just a tap on the good ol' 'board i find myself doing regularly (the electricsheep.org screensaver uses this (actually up and down arrow) to rate and morph their screensavers

[Paver]

Are you suggesting a keyboard shortcut for rating pictures or are you suggesting a thumbs-up/thumbs-down binary rating system?

If the former, I believe there are issues with mapping the keyboard to web pages.  There's a thread somewhere about using the keyboard to move from photo to photo that discusses such keyboard issues.