Cookies do not identify people, but rather they are defined themselves by a combination of a computer, a user account, and a browser. Cookies may be either “persistent” cookies or “session” cookies. A persistent cookie remains valid until its expiry date (unless deleted by the user before the expiry date). A session cookie, on the other hand, will expire at the end of the user session, when the web browser is closed.
Most browsers allow you to refuse to accept cookies by clicking on the Tools tab and changing the ‘Privacy’ options. Blocking all cookies will, however, have a negative impact upon the usability of many websites.
You may also choose to delete cookies already stored on your computer and different browsers require different actions.
For Internet Explorer, you must manually delete cookie files (instructions are found at http://support.microsoft.com/kb/278835);
In Firefox, you can delete cookies by, first ensuring that cookies are to be deleted when you “clear private data” (this setting can be changed by clicking “Tools”, “Options” and “Settings” in the “Private Data” box) and then clicking “Clear private data” in the “Tools” menu. Doing this may have a negative impact on the usability of many websites you visit.