I have modified the web.config to enable form authentication

<authentication mode="Forms">
      <forms name=".Default" loginUrl="Default.aspx"/>
    </authentication>
    <authorization>
      <deny users="?"/>
      <allow users="*"/>
    </authorization>

I tested few day is no problem.  But today I run the following code in a button as few time

FormsAuthentication.SignOut(); 

Then I remove the code and run again.  My web layout cracked.  Seem all image and css cannot be download.  But it still can be debug.

When I changed the authentication from "Froms" to "Windows" in web.config, my web layout return to normal.  But I changed the authentication from "Windows" to "Forms" again, the web layout still cracked even I delete all cookies in IE and reboot my PC.  I try to change to use IIS, the web layout return to normal.

I think the Visual Studio Development Server Cracked Somthing.  Now I want to know how to repair it.

 Thank you.

Hi,

When you use Forms-Based Authentication in your application, the unauthenticated users cannot access the protect files or folder.

In your case, you can try to configure the web.config to grant all users access to your image and css folders.

For more information, see http://support.microsoft.com/kb/316871/en-us

I hope this helps.