First off you have your #mainWrapper set to 950px wide BUT your main page image is too wide. So most settings are overtaken by this erroneous mismatch.
Resize the image so that it fits into the space available, your l & r columns are set to 150px so 950-300=650px and give a bit for padding & margins.
Your image is currently at photobucket???
place it on your server and it looks to be about 75px too wide allowing for margins & padding that is present.
Do this first and things may begin responding correctly