Using eye tracking to understand the usability of user interfaces is something that's been around for a few years now, but it is still being understood by researchers. Through specialized eye tracking software, you can better see how users visually "enter" a website (or any graphical user interface), navigate the page, and where they focus. First I want to discuss the research and significance for eye-tracking software, then I want to discuss each of these elements in turn.

Research on eye tracking dates back to research on how people read pages in general. Early researchers found that--as common sense would imply--readers are attracted to certain visual stimuli, like bright colors or certain shapes and orientations. This isn't too hard to imagine, as we all know our eyes tend to naturally float towards highlighted areas on a page. However, these researchers also found that readers both see an entire page without really looking at it, and they also enter and visually navigate a page according to how they think the page should be laid out.

Seeing the entire page without really looking at it is important. It means that readers will get meta-information first and then begin to narrow down their visual selections according to that meta-information. Meta-information simply means that when users open a web page, without really even reading it, they will know where advertisements are located, where images and visuals are located, and where information and items relating to each other can be found.

As for the second part, users already have some idea of what a page should look like as soon as they open it. They've been trained on certain things. For example, they usually know to find menus on the left or the top. They usually know that there will be an advertisement located along one or both of the sides of the page (as on this one).

The combination of these two things means that you should design a page so that it meets the user's expectations, and so that they quickly see what you want them to see. Now how do you find out what they're seeing?

Eye tracking applications, such as GazeTracker in association with ERICA (Eye-Gaze Response Computer Aid), EyeLink 2000, or faceLab produce a log of where a user's gaze either moves or is sustained on a page. To understand what a user is fixating on, you need to understand where the user's gaze is sustained for a brief period of time. Those locations display what user's are paying attention to--reading or spending a moment to understand--on the page. Further, understanding the path of their gaze will help you understand how they are visually traveling on a page.

Once you've conducted these tests (using task-based testing) you can use the results to orient information you want your user's to see. All in all, eye-tracking studies are one of the best measurements used for determining the usability of a website.