How to replicate the "popup" messages seen in SE sites?
<p>StackOverflow and other sites in the SE Network have nifty things that pop up with messages, for example, when you click on an upvote link while not logged in. I'm not sure what this sort of thing is called, though.</p>

<p>I'm assuming that this is done with CSS somewhere, but looking at the source of the pages with a view to reverse engineering it, it doesn't seem like the buttons are actually links.</p>

<p>Using C# and ASP.NET, how could I emulate this sort of functionality?</p>
