In my opinion it looks perfectly fine.
You have to be a little bit careful about expanding it because
it may put too much space between objects on the screen.
You can experiment with some small size changes to see what happens.
In the file called:
You will see this at the beginning ...
margin: 0 auto;
/* the auto value on the sides, coupled with the width, centers the layout */
800 pixels (800px) is the width of the main container.
Try changing that to 960px;
and see what happens.
I didn't look far enough to see if all other sections will expand by percent.
But just that small change might make it look better to you.