The definition of cookies below is taken from an excerpt from Wikipedia (the full page can be accessed here http://en.wikipedia.org/wiki/HTTP_cookie)
A cookie, also known as an HTTP cookie, web cookie, or browser cookie, is usually a small piece of data sent from a website and stored in a user’s web browser while a user is browsing a website. When the user browses the same website in the future, the data stored in the cookie can be retrieved by the website to notify the website of the user’s previous activity. Cookies were designed to be a reliable mechanism for websites to remember the state of the website or activity the user had taken in the past. This can include clicking particular buttons, logging in, or a record of which pages were visited by the user even months or years ago.
Although cookies cannot carry viruses, and cannot install malware on the host computer, tracking cookies and especially third-party tracking cookies are commonly used as ways to compile long-term records of individuals’ browsing histories.
Other kinds of cookies perform essential functions in the modern Web. Perhaps most importantly, authentication cookies are the most common method used by web servers to know whether the user is logged in or not, and which account they are logged in under. Without such a mechanism, the site would not know whether to send a page full of sensitive information, or a message saying “sorry, you need to log in”. The security of an authentication cookie generally depends on the security of the issuing website and the user’s web browser.
We are using cookies supplied by Google Analytics to help provide information on visitors, page views, the number of people visiting our site and also the type of browser that is being used. This helps us create a better viewing experience for our users by allowing us to ensure that the right information and viewing elements are delivered correctly.
We may also incorporate Google AdSense too in order to help bring you relevant advert information. This is provided by a third-party provider (Google) and is done so to offer relevant and valid adverts.
For any e-commerce or payment mechanisms cookies are used to store item purchases for the session of your visit. A cookie may also be placed to store your username to help your shopping experience on your next visit.
Most browsers allow you to refuse to accept cookies. For example:
(1) in Internet Explorer you can refuse all cookies by clicking “Tools”, “Internet Options”, “Privacy”, and selecting “Block all cookies” using the sliding selector
(2) in Firefox you can block all cookies by clicking “Tools”, “Options”, and un-checking “Accept cookies from sites” in the “Privacy” box.
Blocking all cookies will, however, have a negative impact upon the usability of many websites
Alternatively, you can follow the guide for opting out of Google Analytics tracking code here – https://tools.google.com/dlpage/gaoptout
You can also delete cookies already stored on your computer:
(1) in Internet Explorer, you must manually delete cookie files;
(2) 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.
Obviously, doing this may have a negative impact on the usability of many websites.