If people aren't taking some specific action on your site that you want them to take, such as making a purchase or signing up for your newsletter(conversion), you may be making it too hard for them to do so. The path to purchasing or signing up may be full of confusing signposts, with poor usability being one of the main reasons people are failing to complete actions on your site. Although complete usability testing is the best way to identify usability issues for real, your web analytics tools can identify issues for further investigation. Creating a more usable conversion path-that is, the path that takes people from your landing page through to a purchase-can make a double-digit difference in sales. My talk at D4DBoston 2011 focused on metrics that show you something is off with your conversion path, and examples of great usability and smooth conversion paths from some recent work.
Some key points:
Conversion optimization is a multi-pronged approach, one that involves not just marketing strategy, marketing communications, and creative but great usability. An easy-to-navigate site is like an easy-to-navigate store: it keeps visitors coming back.