WebGL is a binding of OpenGL ES 2.0 for Javascript. It lets web pages do fast 3D graphics in the browser. The spec is still a work-in-progress, and support is only starting to appear in browsers. None of the regular releases support it yet, so you may need a nightly build.

Mozilla Minefield For WebGL:
Firefox nightly builds support WebGL. You can download those here

However, you need to turn on WebGL manually in the configuration. Type about:config in the address bar, then search for "webgl" and change the value of webgl.enabled_for_all_sites to true.