<div class="outerdiv">
  <div class="outerdivleft">
    ... Update Panel Left ...
  </div>
  <div class="outerdivright">
    ... Update Panel Right ...
  </div>
</div>

.outerdiv div { float: right; }
.outerdiv div:first-child { float: left }

.outerdiv div:first-child {float:left;}
.outerdiv div:last-child {float:right;}