Can anyone point me in the right direction for any turotials and/or advice into making a login screen. I have clients that use my domain to log into their site. In short, this is what I want to happen.

After an intro, a login screen will be displayed. Then, depending on the user, the 'enter click' will take them to a corresponding URL.

Does this mean interaction with txt files or something similar? If so, keep in mind that I have no experience with the topic.

Thank you very much!