We use a unique session id in a cookie file stored on your computer while you are signed in. This cookie expires after about 30 minutes of inactivity or when you sign out.
We mostly use temporary cookie files that expire automatically after each session, except when you use the automatic sign in-function which will store a small file on your computer.
In some cases we use popup-windows. If your browser use a popup-blocker, see the specific browser’s reference manual on how to temporary allow popup-windows.