When I code <script>window.history.back();</script> on a page due to a data validation problem, all browsers except Firefox redisplay the filled-out form page.
Firefox did not used to do this. I do not change browser settings from default to get this unfortunate behavior. This may mean Firefox is more secure, but only on a public computer. On a private computer, this sucks.
See if this helps you. https://developer.mozilla.org/en-US/docs/Web/API/Window.history
If not, try posting at the Web Development / Standards Evangelism forum at mozillaZine. The helpers over there are more knowledgeable about web page development issues with Firefox. http://forums.mozillazine.org/viewforum.php?f=25 You'll need to register and login to be able to post in that forum.
Do you allow caching of the form page? Firefox usually will go back to a cached page and show it just like it was. This article covers some of the scenarios for pages being and not being cached: https://developer.mozilla.org/en-US/docs/Using_Firefox_1.5_caching