input{}{background-color:gray}
button{}{margin-top:70px;width:50px}
</style>
<!-- by Go_Rush(阿舜) from http://ashun.cnblogs.com/ --->
<div id="a1">
divdiv
<span>
spanspan
<h2>ttttt</h2>
</span>
<input>
</div>
<script>
function f(){
var rule="#a1 *{background-color:red}";
var index=document.styleSheets[0].cssRules.length;
document.styleSheets[0].insertRule(rule, index);
}
</script>
<button onclick=f()>转</button>
