All websites hosted on Swedish territory are forced by law to inform their users about cookies and how they're used.
A cookie is a variable that is stored in the users browser. This let website owners store useful data to enhance the experience for the user. For example, a lot of websites which let you login to some sort of account usually have the most recent used username filled out already. This is to save you some extra seconds while logging on.
We use the IP address of a user to keep track of what URLs he or she has added. To handle users with dynamic IP addresses, we store a cookie that lasts for 6 months, containing a unique ID for the user. This is required for the this page.