attempt to liquid design, correct?

Please check this site.
http://www.blackout.gr/teuxh.php
http://www.blackout.gr/keimena/90

It's an attempt to make it liquid. I wanted to tell me if this is the
case, or if it needs improvements.

The main page has 3 divs.

div.leftcol {float:left;width:18%;margin-left:.6em;}
div.rightcol {float:right;width:20%;margin:0 .6em 0 1%;}
div.maincol {width:52%; float:left; text-align:center; margin-left:1%;
border:9px solid #FF8E00;}

Is there a way NOT to explicit set width on .maincol so as to get all
the empty space?
Now I set width:52% on maincol so as for IE6 not to break. But in IE7,
FF, Opera there's a big empty space between .maincol and .rightcol.


thanks