#demo{margin-top:10px; width:500px;}
#demoIzq { border:1px dashed; width:245px; background-color:#EAEAEA; text-align:right; float:left}

#demoDer { border:1px dashed; width:245px; background-color:#EAEAEA; text-align:left; float:right}

select { width:200px; }