A cookie is a file containing an identifier (a string of letters and numbers) that is sent by a web server to a web browser and is stored by the browser. The identifier is then sent back to the server each time the browser requests a page from the server.
Cookies can be used by web servers to identity and track users as they navigate different pages on a website and identify users returning to a website.
Cookies may be either “persistent” cookies or “session” cookies.
A persistent cookie consists of a text file sent by a web server to a web browser, which will be stored by the browser and will remain valid until its set 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.
Cookies do not contain any information that personally identifies you, but personal information that I store about you may be linked, by me, to the information stored in and obtained from cookies.
Most browsers allow you to refuse to accept cookies. For example:
- in Internet Explorer (version 9) you can block cookies using the cookie handling override settings available by clicking “Tools”, “Internet Options”, “Privacy” and then “Advanced”;
- in Firefox (version 16) you can block all cookies by clicking “Tools”, “Options”, “Privacy”, selecting “Use custom settings for history” from the drop-down menu, and un-ticking “Accept cookies from sites”; and
- in Chrome (version 23), you can block all cookies by accessing the “Customise and control” menu, and clicking “Settings”, “Show advanced settings” and “Content settings”, and then selecting “Block sites from setting any data” under the “Cookies” heading.
Blocking all cookies will, however, have a negative impact upon the usability of many websites.
If you block cookies, you will not be able to use all the features on this website.
You can also delete cookies already stored on your computer. For example:
- in Internet Explorer (version 9), you must manually delete cookie files (you can find instructions for doing so at http://support.microsoft.com/kb/278835);
- in Firefox (version 16), you can delete cookies by clicking “Tools”, “Options”, “Privacy” and then “Show Cookies”, and then clicking “Remove All Cookies”; and
- in Chrome (version 23), you can delete all cookies by accessing the “Customise and control” menu, and clicking “Settings”, “Show advanced settings” and “Clear browsing data”, and then selecting “Delete cookies and other site and plug-in data” before clicking “Clear browsing data”.
Again, doing this may have a negative impact on the usability of many websites.