Bring to the user all the information and tools needed for each step of the process.

As a simple example, workers, failing status information, will tend to maintain heightened pressure on themselves during slow periods, until the moment the work actually runs out.

This will stress and fatigue them unnecessarily, so that when the next rush occurs, they may be lacking the physical and mental reserves to handle it.

• Keep status information up to date and within easy view

Even a higher percentage may have temporary alterations in perception of blue under varying conditions.)

Color Blindness

• Any time you use color to convey information in the interface, you should also use clear, secondary cues to convey the information to those who won't be experiencing any color coding today.

(There are, in fact, significant differences in their effects, but those differences have no real effect on design.) While tritanopia is far more rare, it nonetheless rules out dependence on yellow-blue differentiation without secondary cues.

Secondary cues can consist of anything from the subtlety of gray scale differentiation to having a different graphic or different text label associated with each color presented.

Consistency

• Levels of consistency: The importance of maintaining strict consistency varies.

"Invisible structures" refers to such invisible objects as Microsoft Word's clever little right border that has all kinds of magical properties, if you ever discover it is there.

No amount of study and debate will substitute.

Defaults

• Do not use the word "default" in an application or service.

It typically takes more than one second to acquire the zero key.

They do a fast estimate and, given the variability of water content and bacon thickness, end up with as likely a successful result with a lot less dickering up front, again increasing human efficiency.

• Keep the user occupied

This lets the new user and the user who just wants to get the job done in the quickest way possible and "no-brainer" way through, while still enabling those who want to explore and play what-if a means to wander farther afield.

• Sometimes, however, you have to provide deep ruts.

Sometimes they want to find out what would happen if they carried out some potentially dangerous action.

A study a few years back showed that people in a hazardous environment make no more mistakes than people in a supportive and more visually obvious environment, but they worked a lot slower and a lot more carefully to avoid making errors.

• Always allow a way out.

If you are working with complex transactions using a standard web browser, turn of the menu bar and all of the other irrelevant options, then supply our own landmarks and options.

Fitts’s Law

• The time to acquire a target is a function of the distance to and size of the target.

Fitt's law indicates that the most quickly accessed targets on any computer display are the four corners of the screen, because of their pinning action, and yet they seem to be avoided at all costs by designers.

Use large objects for important functions (Big buttons are faster).

Use the pinning actions of the sides, bottom, top, and corners of your display: A single-row toolbar with tool icons that "bleed" into the edges of the display will be many times faster than a double row of icons with a carefully-applied one-pixel non-clickable edge along the side of the display.

Human-Interface Objects

Human-interface objects are not necessarily the same as objects found in object-oriented systems.

Latency Reduction

• Wherever possible, use multi-threading to push latency into the background.

In practice, all applications and services, no matter how simple, will display a learning curve.

• Limit the Trade-Offs

First, decide which is the most important; then attack both with vigor.

Ease of learning automatically coming at the expense of ease of use is a myth.

Metaphors, Use of

• Choose metaphors well, metaphors that will enable users to instantly grasp the finest details of the conceptual model.

It does so, however, not by acting as a transport mechanism, but as a synchronizer: Documents in the desktop briefcase and the briefcase held on portable media are updated automatically when the portable media is inserted in the machine.

Protect Users’ Work

• Ensure that users never lose their work as a result of error on their part, the vagaries of Internet transmission, or any other reason other than the completely unavoidable, such as sudden loss of power to the client computer.

Do not trust your young eyes to make size and contrast decisions.

Track State

• Because many of our browser-based products exist in a stateless environment, we have the responsibility to track state as needed.

• Whether this is the first time the user has been in the system
• Where the user is
• Where the user is going
• Where the user has been during this session
• Where the user was when they left off in the last session

• State information should be held in a cookie on the client machine during a session with a transaction service, then stored on the server when they log off.

Doctors can be 95% of the way through a complex transaction, log off, log in again six weeks later from another part of the world, and the service will ask them if they want to be taken right back to where they were.

Visible Interfaces

• Avoid invisible navigation.