function writeCookie()
{
    the_cookie = document.cookie;
    if( the_cookie ){
        if( window.devicePixelRatio >= 2 ){
            the_cookie = "pixel_ratio="+window.devicePixelRatio+";"+the_cookie;
            document.cookie = the_cookie;
            window.location = document.location.href;
        }
    }
}

writeCookie();