#contentcolumn{
margin: 0 200px 0 230px; /*Margins for content column. Should be "0 RightColumnWidth 0 LeftColumnWidth*/
}

#leftcolumn{
float: left;
width: 230px; /*Width of left column*/
margin-left: -100%;
background: #ECF0FF;
}

#rightcolumn{
float: left;
width: 200px; /*Width of right column*/
margin-left: -200px; /*Set left marginto -(RightColumnWidth)*/
background: #ECF0FF;
}