Firefox collects data on your behavior and your browser's overall performance so as to provide you with meaningful comparisons and tips, as well as to aggregate the data shared by everyone to make Firefox better for you. This function is turned on by default, but if you don't like the idea of Mozilla keeping an eye on you, it can be disabled under 'Options->Advanced->Data Choices'.
Firefox also uses these collected facts and figures to render a personalized data report of your browsing data, such as how long you've spent on your browser, how many times it has crashed, and even how long it has taken to open (measured in milliseconds). To access this health report, Just go to 'Help->Firefox Health Report'.
