Everything Phreadee said, plus:
It's cramped. There's no white space where white space needs to be. Give the text some breathing room on the right. The stopwatch image seems kind of out of place, and looks bad with the text overlapping it. Never center paragraph text - left justify it and bring the left edge in line with the left side of the nav. The text in the header doesn't contrast very well against the blue background. Same goes for the headers on the sections in the sidebar. HTML tables for design: yuck.
Seems there are some spacing issues, especially in Safari. The diseases page just does not look correct. I agree with stretching photos, that drives me up a wall. With me, it's just an overall balance issue.
Images are stretched and not good. Make larger. Where is the content if this is a website designed to overcome cancer? I'd consider doing a little SEO research and find the best searched terms that you can focus on because there a lot of cancers out there. Good luck.