How to center a horizontal CSS pulldown menu

CSS:
.horizontalcssmenu ul{
margin: 0;
padding: 0;
list-style-type: none;
}
 
/*Top level list items*/
.horizontalcssmenu ul li{
position: relative;
display: inline;
float: left;
 
}
 
/*Top level menu link items style*/
.horizontalcssmenu ul li a{
display: block;
width: 136px; /*Width of top level menu link items*/
padding: 2px 8px;
border: 1px solid #202020;
border-left-width: 0;
text-decoration: none;
background: url(images/menu/menubg.gif) center center repeat-x;
color: black;
font: bold 13px Tahoma;
}
	
/*Sub level menu*/
.horizontalcssmenu ul li ul{
left: 0;
top: 0;
border-top: 1px solid #202020;
position: absolute;
display: block;
visibility: hidden;
z-index: 100;
}
 
/*Sub level menu list items*/
.horizontalcssmenu ul li ul li{
display: inline;
float: none;
}
 
 
/* Sub level menu links style */
.horizontalcssmenu ul li ul li a{
width: 160px; /*width of sub menu levels*/
font-weight: normal;
padding: 2px 5px;
background: #e3f1bd;
border-width: 0 1px 1px 1px;
}
 
.horizontalcssmenu ul li a:hover{
background: url(images/menu/menubgover.gif) center center repeat-x;
}
 
.horizontalcssmenu ul li ul li a:hover{
background: #cde686;
}
 
.horizontalcssmenu .arrowdiv{
position: absolute;
right: 0;
background: transparent url(images/menu/menuarrow.gif) no-repeat center left;
}
 
* html p#iepara{ /*For a paragraph (if any) that immediately follows menu, add 1em top spacing between the two in IE*/
padding-top: 1em;
}
	
/* Holly Hack for IE \*/
* html .horizontalcssmenu ul li { float: left; height: 1%; }
* html .horizontalcssmenu ul li a { height: 1%; }
/* End */
 
HTML:
Head:
<!--Menu Script-->
<link rel="stylesheet" type="text/css" href="menu.css" />
<script type="text/javascript" src="Scripts/menu.js"></script>
<style type="text/css">
 
Body:
<table width="766" border="0" align="center">
  <tr bgcolor="#FFFFFF">
    <th align="center" nowrap="nowrap" class="horizontalcssmenu">
      <ul id="cssmenu1">
		<li style="border-left: 1px solid #202020;"><a href="index.html">Home</a></li>
		<li><a href="#" >Machines</a>
          <ul>
		    <li><a href="polytherm.html">Polytherm 3000-5</a></li>
          </ul>
        </li>
		<li><a href="#">Products</a>
	     <ul>
    	  <li><a href="VanityBowls.html">Vanity Bowls</a></li>
    	  <li><a href="FeaturedProjects.html">Featured Projects</a></li>
    	 </ul>
		</li>
		<li><a href="#">Support</a>
         <ul>
          <li><a href="Forum/index.php">Forum</a></li>
          <li><a href="onlinepayments.html">Online Payments</a></li>
          <li><a href="contact.php">Contact Us</a></li>
		 </ul>
        </li>
		<li><a href="#">Company</a>
    	 <ul>
    	  <li><a href="aboutus.html">About Us</a></li>
    	  <li><a href="history.html">History</a></li>
		  <li><a href="gallery.php">Project Gallery</a></li>
		  <li><a href="contact.php">Contact Us</a></li>
	     </ul>
		</li>
	  </ul>
	  <br style="clear: left;" />      </th>
  </tr>
</table>
 
Javascript:
var cssmenuids=["cssmenu1"] //Enter id(s) of CSS Horizontal UL menus, separated by commas
var csssubmenuoffset=-1 //Offset of submenus from main menu. Default is 0 pixels.
 
function createcssmenu2(){
for (var i=0; i<cssmenuids.length; i++){
  var ultags=document.getElementById(cssmenuids[i]).getElementsByTagName("ul")
    for (var t=0; t<ultags.length; t++){
			ultags[t].style.top=ultags[t].parentNode.offsetHeight+csssubmenuoffset+"px"
    	var spanref=document.createElement("span")
			spanref.className="arrowdiv"
			spanref.innerHTML="&nbsp;&nbsp;&nbsp;&nbsp;"
			ultags[t].parentNode.getElementsByTagName("a")[0].appendChild(spanref)
    	ultags[t].parentNode.onmouseover=function(){
					this.style.zIndex=100
    	this.getElementsByTagName("ul")[0].style.visibility="visible"
					this.getElementsByTagName("ul")[0].style.zIndex=0
    	}
    	ultags[t].parentNode.onmouseout=function(){
					this.style.zIndex=0
					this.getElementsByTagName("ul")[0].style.visibility="hidden"
					this.getElementsByTagName("ul")[0].style.zIndex=100
    	}
    }
  }
}
 
if (window.addEventListener)
window.addEventListener("load", createcssmenu2, false)
else if (window.attachEvent)
window.attachEvent("onload", createcssmenu2)