When Testing After your application is functioning, but before full deployment, it's time to think about debugging and handling errors. This is a very subtle but important step.
Nothing looks worse to a user than seeing an error page.
Look at how your pages interact. Users can bookmark pages or type in URLs by hand, and you don't want them to see error messages. These checks can make the difference between a solid, polished application and a shaky-looking one. Another way to prevent a user from getting an error is with error catching. This code catches any errors and displays an error page.