Safari Reader (or the Chrome/FF extensions like it, or the readability bookmarklet) fix it nicely (and many other sites like it).

I think that's a foreground, actually. :)

I will check into that. It's just a stock Tumblr theme, and my screen is usually dirty, so I didn't even notice!

EDIT: just plain white now. Thanks! For anyone who is curious what he's talking about, the theme I'm using had this set as a fixed background: http://static.tumblr.com/nfoxfxu/r5fl3h6w1/bg.jpg