If you navigate to a new fragment ID (#foo) and then go back, the location object doesn't properly reflect the previous location via location.href or location.hash. See attached test case.
Created attachment 7884 [details]
test case that demonstrates the problem
I'm pretty sure this bug is a duplicate of Bug 6309. If you read through that bug's comments, you'll see that the only issue left is the one described here.
This bug was fixed when Bug 6309 was fixed, so marking it as a duplicate.
*** This bug has been marked as a duplicate of 6309 ***