One of the most significant changes to the user interface for Firefox 4 was the rolling of the old menu items into one button, something we have called on this blog the “combined menu.” We’ve addressed the impact of this change in other posts, such as this one.  We thought of one obvious follow-up: how often do people ‘bounce away’ from the combined menu before clicking something in it?

We define the bounce rate as this: given a user clicking the combined menu button, what is the proportion of instances where users do not click on one of the menu items? We built a small NumPy library to help us analyze the sequence of user-browser interactions.

44% of users clicked something other than a menu item after having clicked the Firefox button, while 56% clicked on a succeeding menu item. These percentages do not change even if we throw out the first few instances of every user clicking on the Firefox button (new Beta users are likely curious about the new menu layout, so try it out).

The bounce rate for this study has gone up since the last version (where about 38% of button clicks led to bounces).  One possible explanation points to the handful new items added to the combined menu since the last beta interface study.  The additional cognitive load might lead to more bounces.

We are currently working on calculating the bounce rate for the pre-combined menu UI.  Stay tuned for that.