This is intended to be advice for startups, but a lot of the comments about product development and measuring success seemed relevant to me for (web-focussed) product development in general.
Nobody needs to convince you that it’s important to test your website’s design and interaction with the people who will use it, right? But if that’s all you do, you’re missing out on feedback about the most important part of your site: the content.
Whether the purpose of your site is to convince people to do something, to buy something, or simply to inform, testing only whether they can find information or complete transactions is a missed opportunity: Is the content appropriate for the audience? Can they read and understand what you’ve written?
From A List Apart:Testing Content