My page takes quite sometime to load a variety of controls and menu images. I want to show a popup window with progress bar on it. The user must not be able to access the original page on the web-browser when this popup is showing.
When the page has loaded completely, this popup must disappear. How to do this?
You can have a div that covers the whole screen and in the window.load handler hide that element, but I agree with the comment above. Don't do that to your users.
The easiest way to do this would be with an overlay -- an absolutely-positioned <div> that covers the entire page and has a high z-index. Once your page has finished loading (i.e. the loaded event fires) then you can remove the <div>.
A rough example for styling purposes:
<html>
<head>
<style type="text/css">
#loading-overlay { position: absolute; top: 0; left: 0; right: 0; bottom: 0; background-color: #000; opacity: 0.7; }
#loading-message { position: absolute; width: 400px; height: 100px; line-height: 100px; background-color: #fff; text-align: center; font-size: 1.2em; left: 50%; top: 50%; margin-left: -200px; margin-top: -50px; }
</style>
</head>
<body>
<div id="loading-overlay"></div>
<div id="loading-message">Loading page, please wait...</div>
<!-- rest of page -->
<p>The rest of the page goes here...</p>
</body>
</html>
Be aware that controls may have their own "loaded" event (e.g. <img> tags do), which may fire after the page has completely finished. You would have to experiment to be certain.
This is a custom one I've used on one of my Custom Cloud Applications: NGEN Preload Screen
View the source for body.onload action...
Feel free to use it at your leisure...