xml提交的URL参数不能用绝对路径吗？

http://forum.csdn.net/SList/Ajaxfunction Fun_PostData(url,Body)
{
try{
         var xml = new ActiveXObject("Microsoft.XMLHTTP");
        
         xml.open("POST",url,false);
        
        
         xml.setRequestHeader("Content-Length",unescape(Body).length);
          xml.setRequestHeader("Content-Type","application/x-www-form-urlencoded");
        
         xml.setRequestHeader( "encoding", "gb2312 "); 
         xml.send(Body);
        
         return xml.responseText; 
}
catch(e){
                 d.write('为了你能正确使用本系统，请将你的IE版本升级到5.01以上。');
                 return '';
}
}以下是正确调用，用了test.asp
function Fun_GetPostData(){
        var urlid=getCookie("urlid_cookies");
        var url='test.asp?idstr='+urlid+'';
        
        var str = ''; 
        var responsevalue=Fun_PostData(url,str);
        if (responsevalue!='')
        {
                
                favorites_body.innerHTML=responsevalue;
                
        }
        
}
以下把test.asp换成http://www.test.com/test.asp，执行起来总是提示“为了你能正确使用本系统，请将你的IE版本升级到5.01以上”
function Fun_GetPostData(){
        var urlid=getCookie("urlid_cookies");
        var url='http://www.test.com/test.asp?idstr='+urlid+'';
        
        var str = ''; 
        var responsevalue=Fun_PostData(url,str);
        if (responsevalue!='')
        {
                
                favorites_body.innerHTML=responsevalue;
                
        }
        
}请问是什么原因咯？