Wanted to add that I've found this specific to use cases where document.domain is set in config. The issue can be easily reproduced in any IE browser with a simple test such as: http://gist.github.com/528661. This one generates 2 extra history states, more can be created by adding more iframe calls (ie, tweetBoxes).
- [twitter-dev] anywhere back button bug in IE dndrnkrd
- [twitter-dev] Re: anywhere back button bug in IE dndrnkrd