More div

Make CSS as

#upleft { 
   width:100px; 
   height: 300px; 
   background:red; float:left; 
}
 
#upright { 
   width:300px; 
   height:200px; 
   background:blue; 
   float:left
}
#below { 
   height:300px; 
   width:400px; 
   background:green 
}
 
And in HTML
 
<div id="upleft"></div>
<div id="upright"></div>
<div id="below"></div>