This post is about usability, and yes, the (arrogant) usability guru Jakob Nielsen is the guy who listed the Top 10 web design mistakes of 2005.

No matter what's your role in the agency, remember usability does affect online marketing. A great concept can fail if the text is too small, the website takes a life time to load or only Explorer users can experience it. So read this article carefully and make sure to avoid doing the same mistakes.