var xmlHttp;

function AjaxRequest(httpMethod,command,callback){
    xmlHttp=GetXmlHttpObject();
    if (xmlHttp==null)
    {
        alert ("Your browser does not support AJAX!");
        return;
    } 
    xmlHttp.onreadystatechange=callback;
    xmlHttp.open(httpMethod,command,true);
    xmlHttp.send(null);
}

function GetXmlHttpObject()
{
    var xmlHttp=null;
    try
    {
        // Firefox, Opera 8.0+, Safari
        xmlHttp=new XMLHttpRequest();
    }
    catch (e)
    {
        // Internet Explorer
        try
        {
            xmlHttp=new ActiveXObject("Msxml2.XMLHTTP");
        }
        catch (e)
        {
            xmlHttp=new ActiveXObject("Microsoft.XMLHTTP");
        }
    }
    return xmlHttp;
}