Mac Internet Explorer Enabling / Disabling Cookies

A cookie (also called a Persistent Client Side State Object) is a little piece of information handed to a WWW client by a WWW server, containing information that can be retrieved by the server later. For instance, a server can hand your browser a cookie when you fill out a form stating your preferences for visiting that server. Then, the next time you visit the site, the server can read your preferences from the cookie and customize the appearance of the Web site to your preferences.

Do they pose a risk to you?
Keep in mind that these systems mostly rely on information you supply anyway. In a context where you are a regular user or customer, cookies probably work to your benefit. Cookies are often used only to track a specific Web session, and may expire after that visit. They are supposed to be limited to only exchange cookie information with the Web site that originated the cookie data - they use host domain names to manage the data and to limit access to it. Cookies might be saving a flag that says you already entered your password and were validated -- so you don't have to enter the data for every page you access in a given session or perhaps even for future sessions.