They are a tiny text file. Open Windows Explorer and find a folder called Cookies. This contains your cookies, look down and you'll find a file called something like your name followed by @answerbank.co.txt, open that with Notepad and you'll see there's one line of numbers and text.
When you go to Answerbank it looks for that cookie file, and from that it can identify you, and log you in so you don't have to put in your username and password.
If you delete the file, then next time you come to this site you'll have to logon again. They save time and effort, but if you use a shared machine anyone else coming to this site will be logged on with your user name



