Firefox 4 added the security feature that disables alert/ prompt/ confirm when a user checks "Prevent page from creating additional dialog.." This breaks number of applications and one can even circumvent it by using third party alert dialog boxes. I would have expected Firefox to provide a safe site feature similar to block pop-up windows or even use the same list to not display this check box, so that legit sites and applications can continue to run without any glitches. We are at crossroads on whether to replace all our alert with jquery alert or not support Firefox 4 at all or assume that our users will correctly set the property dom.successive_dialog_time_limit to 0 in about:config. I am still optimistic that Firefox developers will realize the value in supporting a safe list. However, till that time comes, I would like my browser detection page to check if this property was set correctly by the user, and if so allow them to use my web pages. Note: many of the users are not as computer savvy and would find it extremely difficult to make changes in about:config themselves. The downside is that this will force them to turn the security feature for all websites.