ELMAH is an open source project whose purpose is to log and report unhandled exceptions in ASP.NET web applications. Since its first public release back in 2004 as a sample to the MSDN article Using HTTP Modules and Handlers to Create Pluggable ASP.NET Components, it has gained many new features and extended its support for newer ASP.NET releases - yet without dropping compatibility with older ones.
This article provides a comprehensive overview of the project as well as a detailed guide about setting it up under different environments.