Get rid of the position:relative;
and replace it with float:left;
and float:right;
.
Example in jsfiddle: http://jsfiddle.net/d9fHP/1/
<html>
<title>
Website Title </title>
<div id="the whole thing" style="float:left; height:100%; width:100%">
<div id="leftThing" style="float:left; width:25%; background-color:blue;">
Left Side Menu
</div>
<div id="content" style="float:left; width:50%; background-color:green;">
Random Content
</div>
<div id="rightThing" style="float:right; width:25%; background-color:yellow;">
Right Side Menu
</div>
</div>
</html>?