In the book Defensive Design for the Web, 37Signals defines defensive design as such: “Design for when things go wrong.”
Gets right to the point, doesn’t it? Defensive design anticipates both user and website error. Then, it tries to prevent those errors and provide help to get the user back on track. Defensive design for the Web usually focuses on the most common points of failure: forms, search, the address bar and server problems.
The underlying premise of defensive design is that it is often easier/cheaper to retain or up-sell existing visitors than acquire new ones. I will paraphrase his example: if your current conversion rate (define as you will) is 2.5% (rough web average) then conversion optimisation to 3% equals an additional 5 customers per 1000 visitors. At 2.5% it would take an additional 200 new visitors to generate 5 new customers. An additional 0.5% conversion rate or acquiring 200 new visitors, which is likely the best ROI?
He then tackles the 'lowest hanging fruit' with illustrative examples (summarised):
* Inline And Contextual Help
Inline help offers pointers on specific items on the page.
Contextual help provides guidance relevant to the current page or process.
* Slow Connections
Plan ahead and have a website that still works when bandwidth shrinks.
* On-Site Search
Anticipate misspellings and typos and turn on-site search into an asset.
* Form Validation And Error Handling
...defensive form design does the following:
---Preserves visitor data
---Highlights errors with clear graphics and text
---Doesn’t make the visitor feel like a criminal
Note: form design and error handling is a deep subject upon which entire books have been written. Forms are serious stuff.
* “Page Not Found” Errors
Great websites customize their “Page not found” area (also called a 404 page), by providing options, explaining what happened or even injecting a little humor into what can otherwise be a frustrating experience.
You don’t have to make the 404 page a work of art. Just make sure that if a detour is required, you do the following:
---Reassure visitors that you’re still there by branding the page.
---At a minimum, link back to the home page.
---Ideally, provide concrete options for getting back on track.
* Detect Holes In Your Defenses
...you can spot subtler issues and their solutions using some basic Web analytics.
---The Checkout Funnel
---The Missing Link (page)
* Avoid Common Mistakes
---Limited Landing Pages
---Limited Browser Compatibility
* Good For The Brand, Good For The Business
Almost any brand can benefit from good customer service. Defensive design lets you deliver great service effortlessly when your customers need it most. It builds sales and makes customers love you. So, hope for the best and plan for the worst.
A great primer on a valuable mindset. I highly recommend that you read and apply.
Having done so, try searching Cre8 as part of your further research as all of the above has been discussed here in more or less detail over the years. What he has written is not new but has been carefully packaged for easy digestion.