For a start you dont need to wrap lists with paragraphs, the list is fine on its own:
<p><ul>
<li>custom website design </li>
<li>domain registration</li>
<li>email & contact forms</li>
<li>e-commerce solutions</li>
<li>updates and maintenance</li>
</ul> </p>
I think your problem is because you have no container div to wrap all the page contents.
Add a div with id="wrapper" around the other divs, give it a set width of 955px (which is 1024x768 with the browser maximised) in the css:
#wrapper { text-align:left; margin: 0 auto; width: 955px; }
I think that should stop the content going off to the right.