var xmlHttpObject = false;

if (typeof XMLHttpRequest != 'undefined') 
{
    xmlHttpObject = new XMLHttpRequest();
}
if (!xmlHttpObject) 
{
    try 
    {
        xmlHttpObject = new ActiveXObject("Msxml2.XMLHTTP");
    }
    catch(e) 
    {
        try 
        {
            xmlHttpObject = new ActiveXObject("Microsoft.XMLHTTP");
        }
        catch(e) 
        {
            xmlHttpObject = null;
        }
    }
}