Ok I can see this is going to be a nice little personal forum with a great motive - but i couldn't agree with Princeton any more.
The cleanest looking thing on your website is probably your ads

When you're dealing with the main alternating colors (alt1,alt2) most of the time it's best to keep them rather close for easy transitioning, but regardless of which route you go - you need to edit the rest of the css accordingly. For example, that text on the orange should not be black nor the links orange, I can't read the text and the links hurt my eyes.