function defCart() {
    if (http_request.readyState != 4 && http_request.readyState != 'complete')
    {
       myload = document.getElementById("loader");
       myload.style.visibility = 'visible';
       myload.style.display = 'block'; 
    } 
             
    if (http_request.readyState == 4 || http_request.readyState == 'complete') {
        if (http_request.status == 200) {
           myload.style.visibility = 'hidden'; 
           if(http_request.responseText != '') {
                rdy = document.getElementById("def_cart_rdy_"+http_request.responseText);
                rdy.style.visibility = 'visible';
           }
        } else {
             loader_img = document.getElementById("loader");
             loader_img.style.backgroundImage = 'url("images/ajax-failure.gif")';
             myload.style.display = 'block'; 
             
        }
    } 
}