The better practice is to center the text one element at a time, rather than at the body level.
<html>
<body>
<div style="margin:0 auto;width:800px;">
<h4 style="text-align:center">Welcome</h4>
<ul>
<li>List item</li>
<li>List item</li>
</ul>
</div>
</body>
</html>
Not only does this give you far better control of your layout, it will also allow you to ONLY center things that you want to.
After seeing your code below, remove the text-align: center; in the #body tag, this should help alleviate the list icons sticking to the left.