Does anyone know why the "sub" list keeps jumping into the content column? It has something to do with the main navigation list at the top of the page, but I cannot figure out for the life of me what is happening.

The CSS and XHTML now is below. Thank you!

Code:
/* 07.11.2003
----------------------------------------------- */
body {
  	margin:0;
  	padding:0;
	text-align: center;
  	background:#fff;
  	font: 76% Verdana,Sans-serif;	
}
	
/* layout 
----------------------------------------------- */
#spinalcord {
	width: 760px;
	margin-left: auto;
	margin-right: auto;
	}
	
#head {
	text-align: left;
	margin: 0;
	}

#content {
	width: 541px;
	line-height: 1.5em;
	text-align: left;
	padding: 0;
	margin: 0;
	margin-left: 215px;
	}

#sidebar {
	float: left;
	width: 200px;
	text-align: left;
	margin: 0;
	padding: 0;
	}

#foot {
	clear: both;
	padding: 5px;
	margin-top: 5px;
	font-size: .8em;
	}
	
	
/* main navigation 
----------------------------------------------- */
#head div {
	width: 516px;
	padding-left: 225px;
	margin: 0;
	border: 1px solid #ccc;
	background: #fff;
	}

#head ul {
	margin: 0;
	padding: 0 0 20px 10px;
	border-bottom: 1px solid #696;
	}

#head ul li {
	margin: 0; 
	padding: 0;
	display: inline;
	list-style-type: none;
	}
	
#head ul a:link, #head ul a:visited {
	float: left;
	font-size: 10px;
	line-height: 14px;
	font-weight: bold;
	margin: 0 10px 4px 10px;
	text-decoration: none;
	color: #9c9;
	}

#head ul a.active:link, #head ul a.active:visited, #head ul a:hover {
	border-bottom: 4px solid #696;
	padding-bottom: 2px;
	background: #fff;
	color: #363;
	}

#head ul a:hover {
	color: #696;
	}
HTML Code:
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<title>Shake a Leg</title>
<link rel="stylesheet" type="text/css" href="/s/low.css" />
<link rel="stylesheet" type="text/css" media="print" href="/s/print.css" />
<link rel="stylesheet" type="text/css" media="screen" href="/s/screen.css" />
<meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1" />
<meta http-equiv="Content-Language" content="en-us" />
<meta name="keywords" content="Shake a Leg" />
<meta name="description" content="Mainstream, complementary and recreational therapeutic services that develop 
independent living skills for individuals who have experienced spinal cord injury and related nervous system disorders." />
<meta name="Copyright" content="2002-2003 Shake a Leg All rights reserved." />
</head>
<body>
<div id="spinalcord"> 
  <div id="head"><a href="/"><img src="sal_logo.gif" alt="Shake of Leg" border="0" /></a> 
    <div> 
      <ul>
        <li><a href="/programs/" class="active">programs</a> </li>
        <li><a href="/events/">events</a></li>
        <li><a href="/news/">news</a></li>
        <li><a href="/resources/">resources</a></li>
        <li><a href="/about/">about sal</a></li>
        <li><a href="/contact/">contact</a></li>
      </ul>
    </div>
  </div>
  <div id="sidebar"> 
    <ul id="sub">
      <li><a href="#">Body Awareness Therapy</a></li>
      <li><a href="#">Adaptive Sailing</a></li>
      <li><a href="#">Body Awareness Therapy For Teens</a></li>
    </ul>
  </div>
  <div id="content"> 
    <p>In 1982, Shake-A-Leg began serving individuals who have experienced spinal 
      cord injuries and related neurological disorders with the Body Awareness 
      Therapy program. The purpose of Body Awareness Therapy is to help participants 
      develop the necessary tools to function at their greatest potential.</p>
    <p>As second-phase therapy, Body Awareness differs in several ways from acute 
      rehabilitation. First, the emphasis is on working with the whole person 
      - mind, body and spirit. Additionally, participants are self-motivated and 
      seek out Shake-A-Leg at a time in their lives when they are ready to take 
      on new challenges.</p>
    <p>The magic of Shake-A-Leg lies in peer-to-peer challenge. Participants with 
      varying years of experience with their disability provide each other with 
      a rare wealth of information. Those with similar injuries teach one another 
      and challenge each other beyond what they thought possible.</p>
  </div>
  <div id="foot">Copyright &copy; 20022003 Shake a Leg</div>
</div>
</body>
</html>