I’d installed the .Net Framework 3.5 successfully.
The ASPNET user had full control to my website directory.
I had a correctly formed web.config in the root directory with customErrors mode=”Off”.

I was getting the following error:

Server Error in ‘/’ Application.
Runtime Error
Description: An application error occurred on the server. The current custom error settings for this application prevent the details of the application error from being viewed remotely (for security reasons). It could, however, be viewed by browsers running on the local server machine.

Details: To enable the details of this specific error message to be viewable on remote machines, please create a <customErrors> tag within a “web.config” configuration file located in the root directory of the current web application. This <customErrors> tag should then have its “mode” attribute set to “Off”.
<!– Web.Config Configuration File –>

<configuration>
<system.web>
<customErrors mode=”Off”/>
</system.web>
</configuration>

Notes: The current error page you are seeing can be replaced by a custom error page by modifying the “defaultRedirect” attribute of the application’s <customErrors> configuration tag to point to a custom error page URL.

<!– Web.Config Configuration File –>

<configuration>
<system.web>
<customErrors mode=”RemoteOnly” defaultRedirect=”mycustompage.htm”/>
</system.web>
</configuration>

I also had no ASP.Net tab in IIS when viewing a website’s properties.

Well, the solution was simple enough. I just ran “aspnet_regiis -i” from a prompt in the v2 framework directory and restarted IIS.  Now I have an ASP.Net tab, and my site the error in server application is gone.

Since 3.5 has no aspnet_regiis, I didn’t think running the v2 one would be the right thing to do, so I spent quite a while messing around with permissions, reinstalling the framework, etc before running regiis. Silly the routes we take, sometimes…