Suppose I have 3 kinds of users and their accessible pages in my ASP.net application are as follows:
(1) User Type-A {Default.aspx, a.aspx, b.aspx and c.aspx},
We have a similar requirement, and make use of the Patterns and Practices Web Client Software Factory. Basically it assists you in creating modules, and allowing you to specify per-page access levels in config based on Role / User details.
Role management in asp.net may help you in this case. Please check this article. You may have to customize this as per your specific requirement. Hope this helps.
Role Manager in ASP.NET
Each of User-Type will be associated with Roles.
You might have a try to use roleship provider and web.sitemap.