<div style="background:#f00;width:300px;height:700px;float:left;margin:50px 0 0 10px;"></div>
<div style="background:#000;width:550px;height:700px;float:left;margin:50px 35px 0 35px;"></div>
<div style="background:#f00;width:300px;height:700px;float:left;margin:50px 0 0 0;"></div>
<div style="clear:both"></div>