I'm having issues using prefixfree, the jquery plugin does not seem to work in internet explorer 9. (maybe it's just some screwed up setting in my browser, I don't know, but prefixfree itself does the job all right: the initial rotate(20deg) is prefixed)
I have set up a jsbin example showing what I mean: http://jsbin.com/ocipel/2/edit
I tested this in chrome and firefox, which work as expected. Any help is greatly appreciated. (oh and it seems prefixfree does not exist as a tag, so I had to split it up into "prefix" and "free", sorry for that)
That's because your prefix-free plugin only runs at pageload. Since the prefix-free plugin parses each stylesheet in your document on pageload, the square is rotated 20deg.
After pageload you give the css property transform another value with javascript, but the prefix-free plugin does not know that. So you should 're-run' the prefix-free plugin after each interval.
EDIT: it seems I do not need the plugin for jQuery 1.8.0+, which auto-prefixed the css properties already, so thanks for making me search again. (anyways I still don't know why it did not work, but it does not have to now)