var js_xmlHttp=false;

function runAjax(){
    js_xmlHttp=new XMLHttpRequest();

    var js_temp1=document.getElementById("id_username").value;
    var js_temp2=document.getElementById("id_password").value;

    var js_data="username="+js_temp1+"&password="+js_temp2;

    js_xmlHttp.open("POST","Display_Ajax.php",true);

    js_xmlHttp.onreadystatechange=function(){
        if(js_xmlHttp.readyState==4 && js_xmlHttp.status==200){
            document.getElementById("id_display").innerHTML=js_xmlHttp.responseText;
        }
    }

    js_xmlHttp.send(js_data);
}