Marcusg;Although advanced solutions using "AJAX", Javascript and WSH (Windows Scripting Host) can be used to design a security system whereby each customer has his own userID and password stored in his registry file. I'd like to suggest a much simpler solution.
If your customer has paid for your eBook, then he should be entitled to all information contained with the eBook (including web content). Therefore your eBooks only need one userID and password (set up as Activ Variables at compile time). For example: If your eBook is called "My Best Secrets" then a build in userID could be "mySecretID" and a password of "LETMEIN".
After a customer buys the eBook it would log onto your web site "secure folder" and use the userID of "mySecretID" and a password "LETMEIN" to access the secure information. All customers who bought the same eBook would use the same userID and password to access the same secure information.
The beauty of this system is that it can be used with a "Try before you Buy" demo eBook so that some information is free. Then, when a customers pays, your eBook can use the built in userID and password to access the restricted information.
Different versions or different eBooks could have different passwords and access different secure folders. And -- because the passwords are "built" into each eBook, they are hidden from the customer so they can't pass them to someone else or be used outside of the eBook itself.
Your gateway "AJAX" website connection code just needs to hand off these built in userID and passwords when it makes the initial connection.
Using such a system allows you to set up folder access with "global" userID and passwords. Then you don't need to bother with keeping track of users or maintaining a user information database with it's associated headaches.
Unfortunately, such a system would not work for a subscription service because you would need to keep track of "currently paid-up" members. If you want to use a subscription service then I'd suggest getting a commercial programmer to setup your security code unless your familiar with "Ajax", Javascript, WSH, PHP and database programing.