<script type="text/javascript">

var checkSubmitFlg = false;

function checkSubmit() {

 if (!checkSubmitFlg) {

// 第一次提交

  checkSubmitFlg = true;

  return true;

 } else {

//重复提交

  alert("Submit again!");

  return false;

 }

}

</script>

//以下三种方式分别调用

<form onsubmit="return checkSubmit();">

<input type="submit" onclick="return checkSubmit();" />

<input type="button" onclick="document.forms[0].action='./test';document.forms[0].submit();return checkSubmit();" />