If all you are trying to do is center your layout then have everything inside it its pretty straight forward. (It would help if you had something online we could see).
#container {
width:770px
margin:0 auto;
}
#leftColumn {
width:200px;
float:left;
}
#rightColumn {
margin:0 0 0 205px;
}
<div id="container">
<div id="leftColumn">
<ul>
<li><a href="">Link Here</a></li>
<li><a href="">Link Here</a></li>
<li><a href="">Link Here</a></li>
<li><a href="">Link Here</a></li>
<li><a href="">Link Here</a></li>
</ul>
</div>
<!-- end #leftColumn -->
<div id="rightColumn">
<p>Sample text paragraph</p>
</div>
<!-- end #rightColumn -->
</div>
<!-- end #container -->