Custom Error handlings

Today, I visited Microsoft's site to view/verify my MCP credentials, which could be acceessed from https://mcp.microsoft.com/authenticate/validatemcp.aspx, when i provided my transcriptID and access code, it exposed error screen which is a bad practice. 

If it is bad practice than what is best practice/solution to avoid this yellow screen. I laughed as Microsoft itself gave solution in ASP.NET to avoid this error screen but didn't use itself. In order to avoid this screen, open your application's web.config file, there is a section named as . By default, it's mode value is "Off" which means that if your application encouter an error, it should display error details to user but safe practice is