I am a real novice at this absolute positioning stuff but with a bit of help from here I did get an absolute positioned left side bar to work, YMMV. I did not put my abs. pos. element in the td tags but just had a div to clear the space. I put the abs. position code at the bottom of the html page as I didn't want the SE to pick up the navigation menu at the top. It was a bit fussy to get the abs. pos. sidebar to center properly. so:
<table width="100%" border="1" cellspacing="0" cellpadding="0" bgcolor="#ffffff">
<tr class='midrow'><td style="width:17.5%;background:#009999;">
<div id="clearleft">
</div>
</td>
..... rest of the page and at the bottom.
</table>
<div id="leftsidebar">
<?php
include("left_sidebar.inc");
?>
</div>
and for the css:
#clearleft {
width:100%;
height:1400px;
overflow:hidden;
background:#009999;
}
#leftsidebar{
position:absolute;
top:320px;
left:15px;
width:15%;
height:1350px;
background:#009999;
text-align:center;
}