As part of offering and providing our services, we use cookies to store and sometimes track non-personal information about users who visit our site. A cookie is a small amount of data that is sent to your browser from a web server and stored on your computer's hard drive. This course requires that you accept cookies. Generally, we use cookies to: (1) Remind us of who you are and to access your account information (stored on our computers) in order to deliver to you a better and more personalized service. This cookie is set when you register or "Sign In" and is modified when you "Sign Out" of our services. (2) Estimate our audience size. Each browser accessing our site is given a unique cookie which is then used to determine the extent of repeat usage, usage by a registered user versus by an unregistered user. (3) Measure certain traffic patterns, which areas of our web site you have visited, and your aggregate visiting patterns. We use this research to understand how our users' habits are similar or different from one another so that we can make each visit to our site more useful. We may use this information to better personalize the content that you and other users will see on our sites.