The best error message is one that you don't have to show!

Avoid errors by providing embedded assistance on more complex controls.

Deep within many of the systems we evaluated lies a complex, and sometimes non-standard UI control feature that is critical to performing an important task.

In the ONC 2014 Edition Summative tests, this control was usually related to the “Clinical information reconciliation task.” The control was usually some type of “Shuttle” widget where the user selects multiple items from one or more lists and places them into a single reconciled list (of Problems, Allergies, and Medications)

When using a complex and/or non-standard UI it is very important to provide a small amount of embedded assistance along with the control.

A short sentence or phrase telling the user to “Select items from List A to add to the reconciled list” goes a very long way to helping them understand what they need to so in order to solve the task at hand. Notice that we said a “small amount” of text.

Be careful... Putting too much text will get in the way of the more experienced user of the control.