Don't use position in CSS. Use Margin/Padding along with float, it works for me.

#rightcontent { float: right; }
#leftcontent { float: left; }
#centercontent { float: inherit; }

Make sure in the XHTML, in order it goes left content, center, right content. See example here: http://ismithop.com/id/mirai that's mine, hope it loads server has some trouble