How do i figure outproblems?

Hi,

I have a problem that a picture show’s up huge on the side.
(http://digitalgestalt.com/portfolio-items/reading-culb/)

now i have two questions:
1. how do i make it go away?
2. what’s the process you went through to figure that out?

btw, it’s a wootheme called withelight.

Thanks,
t.