<style type="text/css">
    #div_wrapper{
        float: left;
        width: 100%;
    }

    #div_content{
        margin-right: 200px; /*Set right margin to RightColumnWidth*/
    }

    #div_right{
        float: left;
        width: 200px; /*Width of right column in pixels*/
        margin-left: -200px; /*Set left margin to -(RightColumnWidth) */
    }
</style>
<div>
    <div id="div_wrapper">
        <div id="div_content">
            Content Column
        </div>
    </div>

    <div id="div_right">
        Right Column
    </div>
    <div style="clear:left"></div>
</div>