It prompts the user a confirmation message before they close the browser window or tab. After that a lightweight window popup jumps up with your preset announcement or message  (in richtext format)

The Advantages >>

1. You can avoid the accidental close of browser window
2. You can tell or mention any message or offers before they navigate away from your website
3. It works not only on closing, but in any type of external navigation (Internal navigation is screened out from this warning)
4. Since it is built on lightweight window support, your message or warning appears very eye-catchy

You can download the plugin from : http://www.sajithmr.com/downloads/onclose-warning.zip

Screen Shot - Warning before close

From the setting page, you can set your rich text message or warning / offer . See the screen shot:

Warning Before Closing

Please feel free to mail me regarding any clarification and upgrade to admin@sajithmr.com

Regards

Sajith

In some cases, if you are in between any work of editing or typing a content, and you wont let the visitor to navigate away from the page without particular condition, say the document is not saved yet, you can block the navigation (even the closing of the browser window) with Javascript.

Here is the javascript code for that:

<script>

window.onbeforeunload = function (evt) {
var message = ‘Are you sure you want to leave?’;
if (typeof evt == ‘undefined’) {
evt = window.event;
}
if (evt) {
evt.returnValue = message;
}
return message;
}

</script>

Just paste this code anywhere in your html page. The condition settings , warning messages are up to you. In the above code, the warning will be displayed when ever a navigation happen (Even closing of browser window happen)

(pic from Binney V.A)