<canvas> was first introduced by Apple for the Mac OS X Dashboard and later implemented in Safari. Gecko-based applications support this new element starting with Gecko 1.8 (i.e. Firefox 1.5 and later). Opera 9 supports as well.
The <canvas> element is part of the WhatWG Web applications 1.0 specification also known as HTML 5.
a demo here: http://www.tapper-ware.net/canvas3d/ (use arrows / space bar to navigate)
about the canvas tag: http://developer.mozilla.org/en/docs/Canvas_tutorial