middle rubber column

gistfile1.html

#container{width:100%;height:20px;}
#left{width:300px;float:left;}
#main{margin:0 200px 0 300px;text-align:right;padding-right:20px;}
#right2{width:200px;float:right;}

<div id="container"> 
  <div id="left">Col1</div> 
  <div id="right2">Col3</div> 
  <div id="main">Rubber col2</div>
</div>