This article covers a topic which is important to almost every application – error messages. The author identifies several common problems with error messages (that they are too vague or difficult to understand). Four guidelines are provided for the design of error messages. Each of these is backed up with a thorough motivation and suggestions for how to implement the guideline. The article ends with links to two excellent references on the subject of error messages.
The article is written in a nice, informal style which makes for light reading. The example error messages shown are well-chosen and help illustrate the points made in the article. What makes the article more compelling as that these are just the kind of unintuitive error messages that one still often sees in mobile applications. Good motivation is provided for all the suggestions made. An interesting article on an aspect of usability which is often neglected.