Disable Anonymous Authentication in IIS cause Error 404.15 - iis-8

Question

As title, I want to disable Anonymous Authentication for my ASP.NET Boilerplate web site (MVC) in IIS Server and use Form Authentication instead. Is it possible to do this because if I disable Anonymous Authentication, my website cause an error "HTTP Error 404.15 - Not Found"
Update 1: Here is my web.config
<system.web>
<globalization culture="auto" uiCulture="auto" />
<compilation debug="true" targetFramework="4.6.1">
<assemblies>
<add assembly="System.Runtime, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a" />
</assemblies>
</compilation>
<httpRuntime targetFramework="4.5.1" />
<customErrors mode="Off">
<error statusCode="404" redirect="~/Error/E404" />
</customErrors>
<httpHandlers>
<add path="Reserved.ReportViewerWebControl.axd" verb="*" type="Microsoft.Reporting.WebForms.HttpHandler, Microsoft.ReportViewer.WebForms, Version=11.0.0.0, Culture=neutral, PublicKeyToken=89845dcd8080cc91" validate="false" />
</httpHandlers>
<authentication mode="Forms" />
</system.web>

Answer 1

I still remember the first time I had to implement Forms Authentication in ASP. All I can say is there is a reason I only do linux based web-development now!
It is a real pain, but this should work if you don't intend on using a database to manage the users.
If you do intend to use a database then prepare yourself for a long road. U need to have the correct MSSQL database for the correct Visual studio tool and they also removed the management interface completely so you either have to design your own or use a tool that is available on the internet somewhere. I still remember I got so frustrated by the whole idea of it, that I literally wrote my own management tool I could deploy on developed sites. If it wasn't on a broken harddrive I would give it to you.
<authentication mode="Forms">
<forms loginUrl="login.aspx" defaultUrl="welcome.aspx">
<credentials passwordFormat="Clear">
<user name="abhishek" password="abhi#123"/>
<user name="Kantesh" password="sinha#123" />
</credentials>
</forms>
</authentication>
<authorization>
<deny users="?"/>
</authorization>
If you plan on using a database to store your users google some tutorials.
The reason why you are getting a 404 is because you are not specifying loginUrl or it is incorrect and pointing to a non-existant page.
Hope this helps

Answer 2

When you disable anonymous access to all pages you cannot let users to see login page as well. what you need to to do is allowing some specific pages like login or register to be accessible.
This might not completely fits for you but you get the idea.
If it doesn't work, try removing the backslash "/" for the "/account/login" and set it like "account/login"
<configuration>
<system.web>
<authentication mode="Forms" />
<authorization>
<deny users="?" /> //this will restrict anonymous user access
</authorization>
</system.web>
<location path="/account/login"> //path here is path to login page
<system.web><authorization><allow users="*" /> // this will allow access to everyone to login page
</authorization></system.web></location>
</configuration>