#wrapper {width:450px; padding:3px;}

/* begin structure */

#prim {float:left; width:300px; height:200px; margin:1px 1px 15px 1px;}
#second {float:left; width:60px; height:200px; margin:1px 1px 15px 1px;}
#terti {width:60px; height:200px; float:right; margin:1px 1px 15px 1px;} 

/* end structure */

#terti {text-align:center}