I'm afraid I can't see why you have those two lines left - there doesn't seem to be any good reason why they should be there. Hopefully Chris will be able to diagnose what's causing this for you when he comes on later.
I can help you with the table width though: type the following at the top of your Header section:
<table align=center width=90%><tr><td>
replacing the 90% with whatever % you want (you may need to experiment).
and then type the following in your Footer section, just before the ending body tag:
That effectively puts your whole page inside an invisible table which will give you more space at the sides to display the background.