Retention is almost the opposite of my conversion rate web design that I focus on daily. But, retention is very important and I revisit it at least once a month. Overall it improves the lifetime value of customers and should be an important KPI (Key Performance Indicator). This is shown in the graph below as Loyal customers spend 19% more money and keep your business going longer.

A lot of the point were made in a nice Web Ex seminar that I recently found via the
Jim Novo website, here is the archived presentation:
Improve Customer Retention: Mastering the Art and Science of Segmentation. This seminar pointed out a lot of tips for Retention Web Design, by helping define the "Potential Value" areas to focus. You can then use analytics to determine what areas of a site need a new user interface, a streamlined navigation, improved content or should you be adding discounts or promotions.
Retention web design is very similar to sales funnel design but there is a larger amount of latency as retention improvements take a longer time to calculate of weeks or months reporting, while sales funnel reporting is daily. This is seen a lot with in content (articles, tools, boards). Here you should receive a lot of feedback from customers and then doing a reactive approach to improve or maintain reasons for returning visitors.
The last part of how Retention Web Design is determined is with Customer Service. This is defined by the companies resources. For example are you pushing clients to a system like "live agent", are you using strictly email support or do you have the call center resources to post your phone number large enough?
This is always and ongoing learning process for all of us. One of the best resources that I have discover is the
Jim Novo website. I recently was recommended this website while listening to
Wizards of the Web on
Webmaster Radio Mondays at 4pm.
I run a children's online educational service - Time4Learning - which provides an online curriculum for kids from preschool to fifth grade. Its important to us that children learn and like learning from our services. Our number one tool in improving the length of time that our students stay with us is improving the information to our members about the education and progress that their children are receiving.