U.Helper

<style type="text/css">
          #hiddendiv {
              display: none
          }
</style>

<script type="text/javascript">
function shide(id){
          object = $('#'+id);
          if(object.is(':hidden')){object.show()}else{object.hide()};
}
</script>

<a href="javascript://" onclick="shide('hiddendiv');">x</a>
<div id="hiddendiv">123</div>

<a href="javascript://" onclick="$('#hiddendiv').toggle();">x</a>
<div style="display: none;" id="hiddendiv">123</div>