It's an internets thing. The animation starts when the image is loaded. There's no mechanism to start or keep them in sync.
(Richy_Thundreds if not thousands of dollars,
Sun 26 Apr 2009, 19:26,
archived)
I am using IE
When it first loaded it was completely out of sync. After I refreshed it was perfect and remained that way. I refreshed again to see if it would go out of sync again and it didn't. I think it depends on which way the wind is blowing.
(FlowerpotNo longer has the vapours thanks to DTH,
Sun 26 Apr 2009, 18:33,
archived)
i've been letting it loop
i think one of them runs very slightly quicker than the other, it goes in and out of sync over time
(Walrus ManThink hippy thoughts,
Sun 26 Apr 2009, 18:34,
archived)
this is ace!
made even better by it going out of sync and Doctorin' The Tardis by the Timelords making it increasing surreal