Matt Cutts talking about ALT attributes
This is the second in his series of video talks published to the Google Webmaster Central blog. I eat this stuff up. I love detailed explanations like this. I feel like I’m armoring up with knowledge 
There’s not much new in this piece for me, to be honest, but it’s still worth a look if you’re not sure about the mysterious use of the ALT tag*.
*everyone calls them “alt tags”, but they’re really an attribute.