function createxhr() {
    if (window.xmlhttprequest) {
        return new xmlhttprequest();
    }
    if (window.activexobject) {
        var msxmls = ['msxml3', 'msxml2', 'microsoft']
        for (var i=0; i < msxmls.length; i++) {
            try {
                return new activexobject(msxmls[i]+'.xmlhttp')
            } catch (e) { }
        }
        throw new error("no xml component installed!")
    }
}

function dopage(obj,url) {
    var xmlhttp = createxhr();
    var xmlhttpurl = url;
    xmlhttp.open("get", xmlhttpurl, true);
    xmlhttp.send(null);
    xmlhttp.onreadystatechange = function () {
        if (xmlhttp.readystate == 4) {
            if (xmlhttp.status == 200) {
      document.getelementbyid(obj).innerhtml=xmlhttp.responsetext;
            }
        }
    }
}

/**
*功能:初始化一个xmlhttp对象
*/
function initajax()
{
var ajax = false;
try
{
   ajax = new activexobject("msxml2.xmlhttp");
}
catch (e)
{
   try
   {
    ajax = new activexobject("microsoft.xmlhttp");
   }
   catch (e)
   {
    ajax = false;
   }
}
//如果一个类型的变量没有定义的话,运用typeof它就将返回undefined
//如果一个类型的变量定义了的话,它就将返回这个变量的类型.
if(!ajax && typeof xmlhttprequest != 'undefined')
{
   ajax = new xmlhttprequest();
}
return ajax;
}