<!DOCTYPE html>
<html>
<body ononline="onFunction()" onoffline="offFunction()">
<p>Open the File menu and click on "Work Offline" to toggle between working online and offline.</p>
<p><strong>Note:</strong> The ononline and onoffline events are only supported in Firefox and Internet Explorer version 8 to 10.</p>
<script>
function onFunction() {
alert ("Your browser is working online.");
}
function offFunction() {
alert ("Your browser is working offline.");
}
</script>
</body>
</html>