Mcafee.com or Skype.com

Hi there guys, I didn’t know anywhere else to ask about this, but I’ve seen a lot of pages lately that use something very similar of what we use to accomplish buy using dhtml layers on and off back the old days, but they do it apparently only with CSS.

The most recent examples I can give you is:
www.mcafee.com and [url=“http://www.skype.com”]www.skype.com

Just rollover on the:
[list]
[]Home & Home Office
[
]Small & Medium Business
[]Enterprise
[
]Partners
[/list] And on the skype page click on the features list at the bottom:

[list=1]
[]Start
[
]Making Call
[*]Etc.
[/list] Anyone knows how can this be done? is there any tutorial around the web?

Thank you for your time and excuse my english…