It's very hard for me to tell if a Firefox window is active or not. So, I often find myself typing into an input box, but nothing happens.
This is because Firefox fails to adhere to the Microsoft Windows style guide by not using the Windows active caption color for the Firefox application window title bar but, instead, always painting it black (which is the Windows default color for a non-active application window).
Please fix by applying SystemColors.ActiveCaptionBrush or SystemColors.ActiveCaptionColor and SystemColors.InactiveCaptionBrush or SystemColors.InactiveCaptionColor, resp., to the Firefox application window title background color.
Please consider this an accessibility issue.