Hide body and when all UI has been rendered show body again, the code looks like this:
<script type="text/javascript">
$.parser.onComplete = function(){
$('body').css('visibility','visible');
};
</script>
<body class="easyui-layout" style="visibility:hidden">
<div region="north" style="height:100px"></div>
<div region="center"></div>
</body>