function hide () {
mydiv = document.getElementById("overlay");
mydiv.style.display = "none"; //to hide it
mydiv = document.getElementById("alerter");
mydiv.style.display = "none"; //to hide it
document.getElementsByTagName("html")[0].style.overflow = "scroll";
}

function popup (alerterheader, alertertext) {
window.scrollTo(0,0);
document.getElementsByTagName("html")[0].style.overflow = "hidden";
mydiv = document.getElementById("overlay");
mydiv.style.display = "block";
mydiv = document.getElementById("alerter");
mydiv.style.display = "block";
document.getElementById("alerttext").innerHTML = alertertext;
document.getElementById("alertheader").innerHTML = alerterheader;
}