ALT vs TITLE

I was getting steamed up because, on the advice of my geek friends I switched to Firefox, and now suddenly I find that my alt attributes are not popping up little messages about the images in my various blogs. Apparently this is because that attribute was never intended to do that, and the specs say use a "title" tag to do it. I never knew that. Thanks to Gadgetopia for sorting this one out for me. Now I have to retrofit all my images, and of course Blogger doesn't automatically add a title attribute to images, but I'm not bitching, really I'm not, I just like to know where I stand!