Can't get detailed error information in ASP.NET MVC website

<customErrors mode="Off"/>

The "Off" must be capitalized correctly.

From "Editing ASP.NET Configuration Files":

Case-Sensitivity

Because tags must be well-formed XML, the tags, subtags, and attributes are case-sensitive. Tag names and attribute names are camel-cased, which means that the first character of a tag name is lowercase and the first letter of any subsequent concatenated word or words is uppercase. In most cases, string attribute values are Pascal-case, which means that the first character is uppercase and the first letter of any subsequent concatenated word or words is uppercase. Exceptions are true and false, which are always lowercase.

Remember kids, you learn something new every day. Even if what you learn is lame.

You may have HandleErrorAttribute global filter in your Global.asax.cs file. Remove that line.

    public static void RegisterGlobalFilters(GlobalFilterCollection filters)    {        filters.Add(new HandleErrorAttribute());    }

A better, long term solution may be to add Elmah to your project, it adds detailed logging to your web project.

Including:

• Logging of nearly all unhandled exceptions.
• A web page to remotely view the entire log of recoded exceptions.
• A web page to remotely view the full details of any one logged exception, including colored stack traces.
• In many cases, you can review the original yellow screen of death that ASP.NET generated for a given exception, even with customErrors mode turned off.
• An e-mail notification of each error at the time it occurs.
• An RSS feed of the last 15 errors from the log.