Head out to http://thornhilllawncare.com/testimonials.php
The graphic that runs along the bottom ("see the difference...our clients include") is the culprit.
I have to minimize that image almost 300 pixels in order to get the side to side scroll bar to vanish. It doesn't make any sense to me why I have to make it so small when, just by eyeballing it, it seems to have plenty of room and I don't know why it goes into "overflow" mode.
What am I doing wrong? Where is the problem that makes the page overflow? If I get rid of the bottom graphic completely, there's no problem. If I slash the width by 300 pixels, no problem. But it shouldn't be an issue at 975px, yet it is. Why?