A cookie is a small text file which is stored on your computer or other device such as mobile phones or tablet devices by a website. Cookies allow a website to remember your preferences whilst visiting the site in order to provide you with a more personalised experience. They help to make websites work efficiently and can allow site owners to track how a site is used to provide useful data for making improvements.
Google Analytics __utma Stores information about your number of visits to the site, including the time of your first visit, the time of your previous visit, and the time of your current visit. - 2 Years
Google Analytics __utmb Used in conjunction with __utmc to track how long you remain on the site. - 30 minutes
Google Analytics __utmc Used in conjunction with __utmb to track how long you remain on the site. - End of session
Google Analytics __utmz Stores how you accessed the site (search engine, link etc). - 6 months
Google provide a tool that allows you to opt out from your visits being tracked by Google Analytics. You can obtain the Google Analytics opt-out tool here.