Help Adjusting Post Width (CSS)

Hello everyone,

I am using WordPress 3.5 and you can find my website here: http://cmlitte.byethost12.com/

The issue I am having is that my page width is slightly larger than my post width allotment, and I’d like to adjust the width of my posts but don’t know how. Here’s a visual example:

Page Width: http://cmlitte.byethost12.com/?page_id=11
Post Width: http://cmlitte.byethost12.com/?p=40

See how my posts only allow 4 thumbnails per row in my galleries as opposed to 5 in my pages? If someone could give me advice on how to fix this, it would be much appreciated.

Thank you!!