I added icons to my navigation toolbar (print, web developer addon, user agent switcher, history, home) between the forward button and the url field. I noticed that if I manually resize my window by dragging the right window edge to the left, items with a relative width stop resizing the same moment the toolbar stops shrinking. If I remove the icons, the page continues to shrink normally. The browser should ignore the width of items on the toolbar at a certain point and continue to shrink the visible area (even if that means some items have to be hidden). Currently, it is almost like there is a bleedover from a menu style that is causing the browser to apply a static width to a single element on any web page that is rendered (usually the last item on the page from what I can tell). I'm guessing a solution would be to hide custom buttons one at a time as the window width no longer allows them to be displayed to preserve the default behavior of the browser.