er { 
  position: absolute;
  top: 0;
  right: 0;
  left: 0;
  height:28px;
  line-height: 24px;
  padding-left: 10px;
  background-color: #444;
  color:#EEE;
}
#tree { 
  position: absolute;
  top: 28px;
  bottom: 0;
  left: 0;
  width:160px;
  padding: 8px;
}
#editor, #preview { 
  position: absolute;
  top: 28px;
  right: 0;
  bottom: 0;
  left: 160px;
  border-left:1px solid #EEE;
}
#preview {
  background-color: #EEE;
  padding:5px;
}
#loader { 
  position: absolute;
  top: 36%;
  right: 40%;
}
.loader