JavaScript show/hide

How to?

[Shingetsu]

Hey all, I'm mostly a php coder, but I tend to use js and trying to learn Ajax.. How exactly does a js show/hide function work?
As an example just post a function with the code initial XD.
I'm not sure, but is it also possible to

GetElementById('ID').elem.style.opacity = x

X being defined in

Function(x)

? Or is that error red code?

[daveVk]

toggle style.display between 'none' and '' if by hide you mean take up no space.

[Shingetsu]

By hide I mean disappear, but have the other elements go up to take it's place.
Kind of how a rollover menu works.

[daveVk]

Good then toggling style.display is the way to go. Changing visibility or opacity (not as well supported) leaves hole where content was.

[Shingetsu]

Thanks!
-solved-