I'm a web developer creating applications for the transport industry. My applications are optimised to run in Firefox and I have a question regarding the latest releases. Some of the users of my applications will often have 2 or more browser windows open at the same time. This is because most of them use multiple monitors and it suits there requirements. But I have noticed that with Firefox 17 and 18 if the user has the same url loaded in two different windows as they often do for valid reasons, that most of the client side functionality is lost in one of the windows. I'm not entirely sure but I think it might be because Firefox is seeing the same element id in both windows and thinks that they are duplicate id's in one window. Could this be the case. Do the latest versions of Firefox do this and if so is this by design. I can solve this issue by keeping my users on Version 16 or earlier and all works as expected. So I'm basically wonder if this is a bug or by design. Any information on this would be greatly appreciated.