Safari / Firefox - BackButton with a AJAX Result behaves different

Hi everybody

I have a problem, may somebody has a hint, how to solve this?
check out http://www.jokerpersonal.ch/vacancies

make a selection
then choose a detail view
hit the back button

a) Safari behaves right
b) Firefox doesn't store the result

Does anybody know, what to do, that Firefox behaves the same like
every other browser does in this case?

Thank you very much!

greetinx