如何防止一直打开网页？
<!DOCTYPE HTML>
<html>
<head>
<script>
var sum=5;
function acc(){
if(sum>0){
document.getElementById("con").innerHTML=sum;
}
else{
window.open("http//:www.baidu.com");
}
sum=sum-1;
}
var i=setInterval("acc()",1000);
function abb(){
window.history.back();
}
</script>
</head>
<body>
<h1>操作成功</h1><br />
<span id="con" >5</span> <h2>秒后回到主页</h2><input type="button" value="返回" onclick="abb()" />
</body>
</html>
