The settings for the warning messages have been removed from the user interface (Bug 513166). You need to change the related security.warn_* prefs directly on the <b>about:config</b> page.<br /> Filter: security.warn To open the <i>about:config</i> page, type <b>about:config</b> in the location (address) bar and press the "<i>Enter</i>" key, just like you type the url of a website to open a website.<br /> If you see a warning then you can confirm that you want to access that page.<br /> *Use the Filter bar at to top of the about:config page to locate a preference more easily. *Preferences that have been modified show as bold (user set). *Preferences can be reset to the default via the right-click context menu if they are user set *Preferences can be changed via the right-click context menu: Modify (String or Integer) or Toggle (Boolean)