dynamic menu

Hi, I'm pretty new to web scripting, (hopefully im in the right usenet
group) and I have recently started a website. Without going into much
detail, I basically wan't to have a small dynamic menu slide down from
the top left corner of the screen when you click a button. I'm really
not a bit sure about where to start. Do I need to learn javascript, or
dhtml, or css, or any comination of those with others not mentioned?
Thanks for all the help in advance,
Keegan Hernandez

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