<!DOCTYPE html>
<html>
<head>
<script>
var timer = 0;
var PERIOD_VISIBLE = 1000;
var PERIOD_NOT_VISIBLE = 60000;
function onLoad() {
timer = setInterval(checkEmail, (document.hidden) ? PERIOD_NOT_VISIBLE : PERIOD_VISIBLE);
if(document.addEventListener) document.addEventListener("visibilitychange", visibilityChanged);
}
function visibilityChanged() {
clearTimeout(timer);
timer = setInterval(checkEmail, (document.hidden) ? PERIOD_NOT_VISIBLE : PERIOD_VISIBLE);
}
function checkEmail() {
}
</script>
</head>
<body onload="onLoad()">
</body>
</html>