How does Stackoverflow do the "You earned a new badge" window?

Answer 1

This is a very simple excersise in HTML, CSS, and DOM manipulation. Take a look at http://jquery.com to add effects, etc...

Using these styles in your css:

#banner
{
    position: fixed;
    top: 0;
    left: 0;
    right: 0;
    background-color: #aaf;
    color: #000;
    font-size: 1.5em;
    padding: .5em;
    z-index: 100;
}

And this HTML on yourpage:

<div id="banner">
    Your text here
    <a href="#" onclick="document.getElementById('banner').style.display = 'none'; return false;">close</a>
</div>

Should do the trick. Play with the styles, etc... to make it look nice.

Answer 2

http://stackoverflow.com/questions/659199/how-to-show-popup-message-like-in-stackoverflow/659243#659243