WebReference.com continues their look at user personalization with the second part of the series - how to validate that the users signing up for your site are valid. (Here's part one, the introduction).

In this article, we will be looking at user authentication. User authentication simply means verifying that a particular user has the right to access a part of our application. Because our application deals with user preferences, access control is even more pertinent especially since multiple users are going to try to access this application at any given time.

As a part of this user validation and customization, they need to create a form that non-human scripts have a harder time using (hopefully weeding them out and getting better user information). The article steps you through a few lines of code that you can use to create a simple image of a four-digit number whose value is placed in a session variable so it can be validated on submission of the form.