<SCRIPT LANGUAGE="JavaScript">
<!--
function GetCookie (name) {             
  var arg = name + "=";
  var alen = arg.length;                
  var clen = document.cookie.length;  
  var i = 0;
  while (i < clen) {       
    var j = i + alen;
    if (document.cookie.substring(i, j) == arg)
      return getCookieVal (j);
    i = document.cookie.indexOf(" ", i) + 1;
    if (i == 0) break; 
  }
  return null;
}

function getCookieVal (offset) {     
  var endstr = document.cookie.indexOf (";", offset);
  if (endstr == -1)
    endstr = document.cookie.length;
  return unescape(document.cookie.substring(offset, endstr));
}

function SetCookie (name, value) {   
  document.cookie = name + "=" + escape (value)
}

function mysubmit()
{
if(GetCookie("times")<1)  
{
alert("谢谢您参与");            
SetCookie("times",1);     
document.myform.submit();   
}
else
{
alert("不要重复提交");  
}
}
//-->
</script> 
<form name=myform action="#">
<p>标识：<input type=text size=20 name=username></p>
<p>口令：<input type=password size=20 name=pwd></p>
<input type=button onclick=mysubmit() value="提交按钮">
</form>