*{margin:0;padding:0}
html,body,div{height:100%}
div{background:#ccc;width:200px;position: relative;transition: .3s;-moz-transition: .3s;-webkit-transition: .3s;-o-transition: .3s;}
div em{position: absolute;width:6px;height:40px;background:#999;top:50%;right:-6px;margin-top:-20px;border-radius:0 5px 5px 0;cursor: pointer;}
div.on{margin-left:-200px}