[Deff]

<script type="text/javascript" src="http://yandex.st/jquery/1.4.4/jquery.min.js"></script>
<div class="block"></div>
<style type="text/css">
.block{
   position: absolute;
   margin-top:23px;
   background-color: #EFEEEE;
   box-shadow: -1px 0 2px 0 rgba(0, 0, 0, 0.5);
   -moz-box-shadow: -1px 0 2px 0 rgba(0, 0, 0, 0.5);
   -webkit-box-shadow: -1px 0 2px 0 rgba(0, 0, 0, 0.5);
   -khtml-box-shadow: -1px 0 2px 0 rgba(0, 0, 0, 0.5);
   display: inline-block;
   min-width: 200px;
   height: 150px;
   border-radius: 10px;
   padding: 5px 20px;
}
.block:after {
  content: '';
  position: absolute;
  width: 0;
  height: 0;
  border: 15px solid;
  color: transparent;
  border-left-color: #EFEEEE;
  left: 100%;
  top: 50%;
  margin-top: -15px;
}
</style>
<script type="text/javascript">
 $("body").append('<style class="append">.block:after{top: 15%;}</style>');
 setTimeout(function(){$("style.append").remove()},2000)
</script>