判断网页是否存在

<script type="text/javascript">

var xmlHttp;

function createXMLHttpRequest(){

try{

xmlHttp=new XMLHttpRequest();

}

catch (e){

try{

xmlHttp=new ActiveXObject("Msxml2.XMLHTTP");

}

catch (e){

try{

xmlHttp=new ActiveXObject("Microsoft.XMLHTTP");

}

catch (e){

alert("您的浏览器不支持AJAX！");

return false;

}

}

}

}

function GetURL(id){

if( id == 1){

var url = document.getElementById('addNoDtsCon').value;

}else if(id == 2){

var url = document.getElementById('addYesDtsCon').value;

}

if(url.trim() == ""){

alert("请输入问题单链接");

return false;

}else{

createXMLHttpRequest();

xmlHttp.onreadystatechange=function(){

if(xmlHttp.readyState==4){

if(xmlHttp.status==200){

alert('该网址存在');

}

else{

alert('该网址不存在');

return false;

};

}

}

try

{

xmlHttp.open("GET",url,true);

xmlHttp.send(null);

}

catch(e)

{

alert("该网址存在");

return false;

}

}

}

</script>