Contrast, Serif and Justify

I was trying to read Locke online, but was annoyed by the fact that the font was dark gray instead of black and sans serif, neither of which is great for extended reading. So I made two bookmarklets: Contrast and Serif. Just drag them to your bookmark bar and click on them to run them on a page. The Contrast one snaps all fonts to white or black (depending on background color) or blue (if it's a link) and adjusts near-black/white page backgrounds to black/white.

Update 1: Justify may also help. And, finally, Reader combines all three functions.

Update 2: Sepia is sometimes nice.

Update 3: See also my Blacker Text extension.