Posizionare 2 quadratini

[E.d.i.73]

Ho provato così vedi se ti va bene,poi i px in piu o in meno li provi te:

 <style>
   div#sinistra{
   width:20px;
   height:100%;
   float:left;
   }
    div#destra{
      width:20px;
    height:100%;
   float:right;
   }
   div#a{
      width:20px;
      height:20px;
      background-color:green;
      float:left;

   }
      div#b{
      width:20px;
      height:20px;
      background-color:green;
      float:right;
   }
   div#c{
   margin-top:550px;
      width:20px;
      height:20px;
      background-color:green;
     float:left;
   }
      div#d{
       margin-top:550px;
      width:20px;
      height:20px;
      background-color:green;
      float:right;
   }
 </style>
   <div id="sinistra">
<div id="a">

</div>
<div id="c">

</div>
</div>
<div id="destra">
<div id="b">

</div>

<div id="d">

</div>
</div>