That’s nothing perfect in the world, no matter how good the application and web site is, that’s still some hole that we may need to handle. By handling that kind of hole, we try to make our application close to perfect.
This powerpoint show that Why we need the error handling, What are error, how the error being handled, type of error, type of error handling.
Advanced ColdFusion - Error Handling (511)
Error Catching with CFERROR and CFCATCH (679)