Have you ever walked up to an office building door and tried to pull it open only to discover it opened by pushing on it? I?ve pushed on doors meant to be pulled, pulled on doors meant to be pushed and walked into doors that were meant to slide, and I?m not alone. I?ve witnessed others having the same trouble - unnecessary trouble.

A door is simple. It poses only two essential questions: Which direction does it move and what do I do to move it? The answers should be apparent by the design, without any need for words or symbols and without any need for trial and error. If a door is meant to be pushed, a vertical plate on the side without the hinges provides a good visual clue. To pull a door open, a handle would be a good indicator.

Knobs are for turning. Buttons are for pushing. Handles are for pulling. We know what to do just by looking at these things ? no pictures or instructions are necessary. Complex things may require explanations but simple things should not. When simple things need pictures, labels, or some other form of instruction, the design has failed.

Usability addresses this relationship between tools and products, and their users. In order for a tool to be effective, it must allow users to accomplish their tasks in the best way possible, and no where is this more apparent than on the Internet.

Usability is defined as a measure of the effectiveness, efficiency and satisfaction with which users can achieve goals when using a given tool ? whether its a door or a software program.

The Five Es of Usability

Effective
Was the task fully completed? Were the user's goals met? Was the task completed successfully? Did the user get the right or correct result? How well was the work done?

Efficient
Was the user able to complete the task quickly? Was the user able to complete the task with a short learning curve?

Engaging
Did the user have a pleasant experience when working on the task? Was the user satisfied by the way in which the application supported his work?

Error tolerant
Did the user interface help the user avoid making errors? Were errors minor rather than major? If the user made an error, did the interface assist him in making a successful recovery?

Easy to learn
Was the user able to work with some certainty because the user interface built on his previous knowledge? Was the interface consistent, so that once the user learned how to use part of the application, he was able to easily learn how to use another part?

Research by User Interface Engineering, Inc shows that people cannot find the information they seek on Web sites about 60% of the time. This can lead to wasted time, reduced productivity, increased frustration, and loss of repeat visits and, ultimately, loss of money.

Studies by Forrester Research estimate several costs of bad web site design. The two most striking are:

Loss of approximately 50% of the potential sales from a web site because visitors can't find what they need

Loss of repeat visits from 40% of the users who do not return to a site when their first visit resulted in a negative experience.

Web site usability guru Jakob Nielsen reports:
"Studies of user behavior on the Web find a low tolerance for difficult designs or slow sites. People don't want to wait. And they don't want to learn how to use a home page. There's no such thing as a training class or a manual for a Web site. People have to be able to grasp the functioning of the site immediately after scanning the home page ? for a few seconds at most."

From the user's perspective usability is important because it can make the difference between performing a task accurately and completely or not, and between enjoying the process or being frustrated by it. From the developer's perspective usability is important because it can mean the difference between the success or failure of a system. From a management point of view, software with poor usability can reduce the productivity of the workforce to a level of performance worse than without the system. (Poor usability ranks right up there with spam in terms of wasted man hours.) In all cases, lack of usability can cost time and effort, and can greatly determine the success or failure of a system. Given a choice, people will tend to use tools that do not tyrannize them ? tools that are user-friendly.

Lynn Harvey is the Creative Director of Carson Park Design, a full service graphic design firm, specializing in print and web site design. She serves as an ambassador for the Arcata Chamber of Commerce, a member of the Eureka Chamber of Commerce, an instructor and consultant with the Small Business Development Center, and an active member of the Redwood Technology Consortium.