防止表单按钮多次提交

1.

<form name=fm method="POST" action="/">
    <p>按钮变灰</p>
    name: <input type="text" name="name"/>
    <input type="button" value="提交" onclick="javascript:{this.disabled=true;document.fm.submit();}">

</form>

2.

<form name=fm method="POST" action="/" >  
  <input type="submit" name="Submit" value="提交" id="submitId" onclick="submit();">  
</form>  
<script language="javascript">  
 function submit()  
 {  
 var submitId=document.getElementById('submitId');  
 submitId.disabled=true;  
 document.fm.submit();  
 setTimeout("submitId.disabled=false;",3000); //代码核心在这里，3秒还原按钮代码  
}  
</script>