Eccolo con le class
codice:
<HTML>
<HEAD>
<style>
.jh{
visibility:hidden; 
}
</style>

<SCRIPT>
function v() {
var s=document.styleSheets[0].rules?document.styleSheets[0].rules:document.styleSheets[0].cssRules;
for(i=0;i<s.length;i++) {
  if(s[i].selectorText==".jh") { 
    s[i].style.visibility=(s[i].style.visibility=="hidden")?"visible":"hidden";
    break;
  }}}
</SCRIPT>
</HEAD>
<BODY>

<p onMouseOver="v()" onMouseOut="v()">asfdaswq</p>

<div class="jh">ddsdadaqda</div>
<div class="jh">ddsdadaqda</div>
</BODY>
</HTML>