In message , at 10:24:12 on Wed, 28 May
2014, Richard J. remarked:
Firefox won't show it at all;

Mine does.

it gives a code 403 error (access denied). Are GIF animations supposed
to run at a particular speed, or does each browser make its own
decision?

There's a delay between frames programmed in, but different browsers
interpret it differently[1] although there seems to be general agreement
that setting the delay to less than 0.02sec (which is 1/50sec) will
cause all browsers to ignore it, which isn't that surprising because
that's the refresh rate of many monitors, and changing the image faster
than that will simply lose frames.

For this particular animation, it's entirely possible that they *want*
the "speeded up" effect.

[1] eg by rounding up anything below 0.06 sec to .10 sec
--
Roland Perry