wireless login

I was wondering how wireless networks are not secured but after you connect and try to go to the internet you have to enter a user name and pass. at a web page and that is the only page you can access until you enter the correct info. so I guise my question is how do you set something like this up. I have searched on google and have found nothing so if someone could point me to an article or explain this to me that would be wonderful.

o all right, gotcha and a lot of fast food places have them around here but thanks for the answer