revision:
The onpagehide event occurs when the user is navigating away from a webpage.
<element onpagehide="script"></element>
script: the name of the script to use when the event has been triggered.
example 1
<body onpagehide="onPageHide()">
<p>Note: Due to various browser settings, this event may not always work as expected.<p/>
<script>
function onPageHide() {
alert ("Thanks, please come back again.");
}
</script>
example 2
<h3 id="hID"></h3>
<script>
document.getElementsByTagName("body")[0].onpagehide = function() {
makeFun()};
function makeFun(){
document.getElementById("hID").innerHTML = "Thank you!";
}
</script>