how to create an area gradually?

[scorpioy]

When we click the down arrow behind the 'Search' button on the top horizontal navigation bar on this page, it will show a window with 'Search Forums', text field, 'Go' button, and 'Advanced Search' link. I know how to create an area to contain other things. But this area is created gradually from the top left to the buttom right, like turning a page. Could someone explain how this is implmented? Thanks.

[JPnyc]

You can't do that with HTML/CSS/Javascript. You'd need either Flash or make the whole page a Java applet

There is a proprietary IE transition that can do something like that, but it'll only work in IE.