This is not a small issue and requires several steps and pages to complete.
Firstly, what system are you using to process? asp? php?
You also need to know in advance what you want your users to achieve - i.e. will they enter personal data?
Either way, you need a back end database - I use MySQL and php for scripting as it's free and simple to use.
Within the database, you will have a table - (users) which will contain as a minimum, a username and password field.
You may also want to add an administration level (or access level) which can be used later on to provide or deny access to certain pages.
A login page will then assign these as server variables which can be checked against each page.
The registration proces is more complex. With my site, I have a registration page which enters the user into the user list, but does not assign user priviledges. The system then fores off an e-mail to the user, asking them to click on a validation link. This link then updates their record and assigns them with user priviledges. This process stops auto-fill bots from filling up your database with god-knows-what.
If you want to see how this works, have a look at
http://forums.x10hosting.com/programming-help/www.freecrm.x10hosting.com
It depends on where you want to go from here?
