Today, 37signals discussed how adding some padding to navigation links improves the user experience.

The end result is a feeling of comfort. It’s just really easy to click the links. It feels like the links are working with you instead of against you.

Its a simple application of Fitt's Law, which commenters were quick to bring up. Fitt's law has been around since 1954, and is used to predict how quickly someone can aim at target and its supported by a lot of experimental data.

The Microsoft Office team used it to analyze the usability of versions of Word and paid special attention to it during the redesign of Office 2007's user interface

First off, most controls in the Ribbon are labeled. This helps discoverability and usability considerably, but it also makes the buttons bigger and easier to target. As your screen resolution increases, the width of the Ribbon also increases, providing room for more labels and larger buttons.

Mezzoblue talks in detail about how it was used when the site went through its fifth redesign. More websites should use this simple technique to increase the clickable area around navigation links and buttons.

A larger clickable area means less precise mouse movement is required to focus on the link. Without impacting the design in any way (the halo is non-visible after all) the usability of the header improves. While the main goal is increased usability in this case, there are positive implications for accessibility as well. Those with motor skill disabilities may have difficulty using a mouse; larger areas to click makes the act easier, which makes a big difference to them.