Cookies are small data files placed on your computer or other device when you visit our websites. The cookies are used to gather information about use of our sites or in some cases, to recognise an existing user when returning. They are commonly used to help websites work efficiently and in a way that you would expect so that you have a good experience when you visit one of our sites. They also help us to improve our websites and make our promotional activity more efficient.
Some cookies are session cookies which means that the cookie will expire when your session finishes. Others are permanent cookies which are stored on your device and will be used to recognise you as a user, the next time you visit. [We currently only use session cookies.]
Generally, cookies can be categorised as:
A persistent cookie - remains on a computer, unless it expires or the cookie cache is cleared. It tracks visitors. Metrics associated with the Google __utma cookie include: first visit (unique visit), last visit (returning visit). This also includes Days and Visits to purchase calculations which afford ecommerce websites with data intelligence around purchasing sales funnels.
__utmb Cookie & __utmc Cookie
These cookies work in tandem to calculate visit length. Google __utmb cookie demarks the exact arrival time, then Google __utmc registers the precise exit time of the user.
Because __utmb counts entrance visits, it is a session cookie, and expires at the end of the session, e.g. when the user leaves the page. A timestamp of 30 minutes must pass before Google cookie __utmc expires. Given__utmc cannot tell if a browser or website session ends. Therefore, if no new page view is recorded in 30 minutes the cookie is expired.
This is a standard 'grace period' in web analytics. Ominture and WebTrends among many others follow the same procedure.
Cookie __utmz monitors the HTTP Referrer and notes where a visitor arrived from, with the referrer siloed into type (Search engine (organic or cpc), direct, social and unaccounted). From the HTTP Referrer the __utmz Cookie also registers, what keyword generated the visit plus geolocation data.
This cookie lasts six months. In tracking terms this Cookie is perhaps the most important as it will tell you about your traffic and help with conversion information such as what source / medium / keyword to attribute for a Goal Conversion.
Google __utmv Cookie lasts "forever". It is a persistant cookie. It is used for segmentation, data experimentation and the __utmv works hand in hand with the __utmz cookie to improve cookie targeting capabilities.
You can block cookies by activating your browser settings. Note though, that if you use browser settings to block cookies, you may not be able to access all or some parts of the sites and our sites may not work as intended. You can find out how to manage and delete cookies by visiting www.allaboutcookies.org.
You can also find out about disabling cookies on the following sites for different browsers:
Internet Explorer - http://support.microsoft.com/kb/278835