html4和html5区别之如何在一个input上添加焦点实现代码

<form> 
<p><label>Username:<input name=search type="text" id="search"></label></p> 
<script type="text/javascript"> 
document.getElementById ('search').focus() 
</script> 
</form> 

<form> 
<p> 
<label>Search:<input name=search autofocus></label> 
</p> 
</form>