I have an error page where users are response.redirected to when an error is encountered on a page. On the error page I have a back button that uses window.history.back to take the user back to where they came from. The problem arises when I window.open page2 from page1 and when an error is found in page2, I am redirecting to the error page. My back button logic in the error page won't work in this case because both page1 and errorpage (in a child window) are open and there is no 'history page' to speak of. How do I fix this?