<script language= "javascript">
function getURL(url) {
var xmlhttp = new ActiveXObject( "Microsoft.XMLHTTP");
xmlhttp.open("GET", url, false);
xmlhttp.send();
if(xmlhttp.readyState==4) {
if(xmlhttp.Status != 200) alert("不存在");
return xmlhttp.Status==200;
}
return false;
}
</script>
<a href= "http://m.survivalescaperooms.com/aaa.asp " onclick= "return getURL(this.href) "> csdn </a>

$.ajax({
url: 'http://some.url.com',
type: 'GET',
complete: function(response) {
if(response.status == 200) {
alert('有效');
} else {
alert('無效');
}
}
});