With Firefox 29.0.1 double clicking on either the left or right hand arrows in the tab bar creates a new tab at the right hand end of the tab bar. This is annoying behaviour that violates standards around UI design single click and double click. A double click should extend the behaviour of the single click rather than doing something completely different (opening a new tab). An example would be , in Word a single click selects a word, a double click selects the sentence and a triple click selects the paragraph. Note that this is a separate issue from double clicking on the tab bar itself to create a new tab. When there are more tabs on the tab bar than will fit in the viewport the tabs scroll sideways so show the tab in use. I can click the left and right arrows at the ends of the tab bar to scroll the bar in that direction to bring a tab that I want to select into view. I believe that double clicking the left arrow would scroll the bar fully right, exposing the left-most tab. Double clicking the right arrow would scroll the bar fully left exposing the right-most tab. This is a logical and expected extension of the behaviour of the single click. Single click - scroll once (seems to be about three tab's worth), double click - scroll all the way. At the moment, if I want to scroll to the left-most tab I have to click the arrow slowly and carefully until I reach it. I used to single click rapidly on the left arrow until the tabs stopped scrolling without having to count how many clicks. It's possible that my rapid single clicks were actually double clicks. Nevertheless, the tab bar would stop scrolling when it reached the end. Now the behaviour is really annoying and unexpected. A double click on the left arrow scrolls the tabs fully right and then fully left and creates a New Tab at the right hand end. Ditto the right hand arrow in the opposite direction. While I can (maybe) see that value of a double click on the tab bar itself creating a new tab, double clicking one of the scroll arrows should not produce a new tab. Double clicks on the tab arrows should scroll the tab bar fully to that end. If the tab bar is already fully scrolled to that end then additional clicks (single, double and triple...) should be ignored. I like the idea of opening a new tab to the right of the one that currently has focus. This should be a right click context menu option.