var imgOnline = document.createElement('img');
imgOnline.id = 'online-image';
imgOnline.style.display = 'none';

window.onload = function(){
    document.body.appendChild(imgOnline);
    setTimeout(OnlineRefersh,1000);
}

function OnlineRefersh(){

    imgOnline.src = '/UpdateOnlineStatus.aspx?r=' + new Date;
    setTimeout(OnlineRefersh,1000*60);
}