When you build a software system, something can go wrong. You have to plan for that. It can be a programming error, an operator error, or a situation you haven’t planned for. I’m pretty sure you have seen web pages giving you cryptic error messages, thus indicating that something went wrong. In many cases, the given error message is useful for a programmer, but seldom for the average web user.
Fatal error:
Call to undefined function: some_function() in
/srv/domain.com/httpdocs/content/mytheme/header.php
on line 42
As a web user, what does this error message tell you? Maybe you can understand it. But can you do something about it? You can’t fix it, you’re left alone on finding your way out, it’s not helping you. Why then show it to you at all? The reason is, it wasn’t intended for you to see it. This error message is only useful for the developer. But he hasn’t planned for exactly this type of situation. Okay, it’s a programming error. But that you have to see this error in a form like this is lack of planning for this type of situation. Everybody knows or can understand that it’s not a good idea to have a web user look at a web page indicating an error like the one I showed you. But it’s still what happens in many cases. Why? Is it laziness on behalf of the developers, lack of good test cases, lack of imagination, lack of time or budget, or not enough knowledge? I think it’s a little of everything. The book Defensive Design for the Web from 37signals might tell you nothing a web developer should know already, but it contains a nice check list at the end to make sure he doesn’t forget to apply his knowledge.
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