I also recently learnt we have a bug making it more restricted than necessary (unless of course you flip that pref):
----- Original Message -----
> On Fri, Jun 24, 2011 at 14:52, Evgeny Demidov
> > in Firefox 6
> > Error: uncaught exception: [Exception... "Failure arg 5
> > [nsIDOMWebGLRenderingContext.texImage2D]" nsresult: "0x80004005
> > (NS_ERROR_FAILURE)" location: "JS frame ::
> > file:///E:/w3/ibiblio/webgl/models/jupiter.html :: <TOP_LEVEL> ::
> > line 164"
> > data: no]
> This is due to same-origin restrictions on file URLs.
> In Firefox you can workaround this by changing
> security.fileuri.strict_origin_policy in about:config