@heagy.com

After seeing the big back button in the latest Firefox beta my first reaction was to turn it back to normal size. My second reaction was to consider the usability advantages. My gut reaction was that it was a small improvement in usability at the expense of a lot of screen real estate.


The button in question


My usability problems with the new big button are this:

• it is, on average, less than 10 pixels wider than the normal sized back button


• it costs about 10 pixels of vertical space from the page viewport


• the gray recess around it (on the Mac) could be confusing to new users

Luckily the implications of the first two can be calculated using Fitt's Law. I calculated the difference between both buttons from the point in the exact center of the viewport as this seemed the most simple way of getting a reasonable result. Also, it takes into consideration that the larger button alters its viewport, and thus affects its own usability.

On a 1024 x 768 screen I found that the larger button would have a 7% speed advantage. This comes at the cost of about 1% the viewport's area. That's more than I expected - I had predicted a difference of less than 5%, which I would have considered insignificant.

Implications

If clicking the back button normally takes a very slow user user two seconds then the new button will take 1.86 seconds. Over time, for such a labored user, the improvement is probably noticeable. So while I will personally continue to shrink the button on my own, I will have to stop complaining about the uselessness of the bigger back button.

Instead I'll complain about the uselessness of the awkwardly-shaped recess it's in.