Another beginner's question

Hi all,

Is there a way to provide a button or link or something for users to be able to zoom in and out of a page- as in the whole page, including images. I've seen a few sites using it- it's something like javascript:zoomIn() and zoomOut(), but as always, when I try it myself, all I get is deeeebbbuuuuuggggg :O Do I need a special script or something? Please help!