Authentication, Authorization, Membership Provider, Role Provider and Profile Provider Settings are directly available in the web.config file if you have created the ASP.NET application by using the Visual Studio 2010.
Based on the error, it looks like they are placed inside some other tag.
Make sure they are directly at root level in Web.Config and not under any other tag. Refer this article on details about the tags and what all can be passed to them:
Web.config File - ASP.NET[
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BTW, visual studio's intellisense in web.Config too will help you out in seeing on what all are available and at what level.