Expansion of dropdown on a web page

[developerquery]

Example

www.microsoft.c om/visualstudio/eng/download

On the above site there are 5 main headings if a user clicks on any plus symbol then the entire detail comes, what is it called?
How to achieve this through html and css?

[gits]

that's an 'accordion' - most common javascript libraries give you the possibility to create such things. like this: http://jquery.bassistance.de/accordion/demo/ one, for example.