Bugmenot is a website that contains usernames en passwords. These accounts are posted by users worlwide. So you will be able to find an account for the website you are trying to visit.
You're browsing the web and you click a link to an article on a site (let's say cyberwarzone.com) but instead of getting the article you get a screen asking you to login or register. Infuriated at the idea of pointlessly registering for yet another site you turn to your good buddy bugmenot.com.
BugMeNot is an internet service that provides usernames and passwords to let Internet users bypass mandatory free registration on websites. Started in August 2003 by an anonymous person, later revealed to be Guy King, it aims to allow Internet users to access websites that have registration walls (for instance, that of The New York Times) without the requirement of compulsory registration. This came in response to the increasing number of websites that request such registration. Many Internet users find this to be an annoyance and a potential source of spam e-mail. BugMeNot itself used to parody these sentiments in its own fake registration form.