[Deff]

<style>
#sidebar {
 height:300px;
 width:67px;
 border:blue solid 1px;
 padding:0;
 }
.content {
margin:0;
 height:100%;
 width:100%;
 border:red solid 3px;
}
</style>
<div id="sidebar">
  <div class="content">
 
  </div>
</div>