Error "Server Error in '/' Application.What does this mean?

How to fix Server Error in 'yourApp' Application

We get asked about this so much it deserves to be shown here. This error doesn't mean a lot except that your site is broken. That's not much help to you figuring out why its broken.
The error page does actually tell you exactly what you need to do to proceed, but for some reason, people don't read it or think that they should not follow these directions. I remember the first time I ran into this error, and I didn't follow the directions, so you aren't alone if that describes you.

Step 1:

• Open the web.config file of your application.
• Find 'customErrors mode="RemoteOnly" '.

Step 2:

Replace "RemoteOnly" with "Off".
*** It is very important that you use capital "O" and lower case "ff", as the web.config file is case sensitive, and if you get that wrong, you will continue to get the same error, even if you managed to fix the original error.

Step 3:

Run your application again, and you should now see a different error with the stack trace. This is the same way you would see the error if it was running on your own computer.

I'm getting "Server Error in '/' Application". What does this mean?

It is an error to use a section registered as allowDefinition='MachineToApplication' beyond application level. This error can be caused by a virtual directory not being configured as an application in IIS.

This happens because you've not configured WebMail Pro virtual directory as an application in your IIS. To do this, run your IIS Manager (Start / Settings / Control Panel / Administrative Tools / Internet Information Services) and open WebMail Pro virtual directory properties, then click Create button in Application Settings section of Virtual Directory tab:



Once you configured the virtual directory as an application, you'll see the following:

* Windows 2000/XP (IIS5):



Windows 2003/2008/Vista (IIS6, IIS7):




If you see the following in the error details:
The WebResource.axd handler must be registered in the configuration to process this request.
that's a well-known problem of IIS 7 if you have ColdFusion installed on your server. To get rid of this error, you need to remove default ColdFusion handler mapping entries from WebMail Pro application through your IIS 7 Manager. Once that's done, ASP.NET starts working properly.