Jacob Nielsen has published 10 common UI design mistakes:
1. Non-Standard GUI Controls (Looking Like a GUI Control Without Being One)
Figure 1: The test user clicked incessantly on the New Customer button to indicate that he was indeed a new customer. Unfortunately, this screen element was not a button at all, but rather a non-clickable heading.
2. Inconsistency
Figure 2: In the second pop-up, the month of March has moved to the left, leaving room for April to appear on the right. This may seem like a convenient shortcut, since there’s no way the user would want a February return date when traveling out in March.
3. No Perceived Affordance (Tiny Click Targets)
“Affordance” means what you can do to an object. For example, a checkbox affords turning on and off, and a slider affords moving up or down. “Perceived affordances” are actions you understand just by looking at the object, before you start using it (or feeling it, if it’s a physical device rather than an on-screen UI element).
An associated problem here is click targets that are so small that users miss and click outside the active area. Even if they originally perceived the associated affordance correctly, users often change their mind and start believing that something isn’t actionable because they think they clicked it and nothing happened.
4. No Feedback (Out to Lunch Without a Progress Indicator)
One of the most basic guidelines for improving a dialog’s usability is to provide feedback:
- Show users the system’s current state.
- Tell users how their commands have been interpreted.
- Tell users what’s happening.
Sites that keep quiet leave users guessing. Often, they guess wrong.
A variant on lack of feedback is when a system fails to notify users that it’s taking a long time to complete an action. Users often think that the application is broken, or they start clicking on new actions.
If you can’t meet the recommended response time limits, say so, and keep users informed about what’s going on:
- If a command takes more than 1 second, show the “busy” cursor. This tells users to hold their horses and not click on anything else until the normal cursor returns.
- If a command takes more than 10 seconds, put up an explicit progress bar, preferably as a percent-done indicator (unless you truly can’t predict how much work is left until the operation is done).
5. Bad Error Messages
Error messages are a special form of feedback: they tell users that something has gone wrong. We’ve known the guidelines for error messages for almost 30 years, and yet many applications still violate them.
The most common guideline violation is when an error message simply says something is wrong, without explaining why and how the user can fix the problem. Such messages leave users stranded.
Informative error messages not only help users fix their current problems, they can also serve as a teachable moment. Typically, users won’t invest time in reading and learning about features, but they will spend the time to understand an error situation if you explain it clearly, because they want to overcome the error.
On the Web, there’s a second common problem with error messages: people overlook them on most Web pages because they’re buried in masses of junk. Obviously, having simpler pages is one way to alleviate this problem, but it’s also necessary to make error messages more prominent in Web-based UIs.
6. Asking for the Same Info Twice
Users shouldn’t have to enter the same information more than once. After all, computers are pretty good at remembering data. The only reason users have to repeat themselves is because programmers get lazy and don’t transfer the answers from one part of the app to another.
7. No Default Values
Defaults help users in many ways. Most importantly, defaults can:
- speed up the interaction by freeing users from having to specify a value if the default is acceptable;
- teach, by example, the type of answer that is appropriate for the question; and
- direct novice users toward a safe or common outcome, by letting them accept the default if they don’t know what else to do.
8. Dumping Users into the App
Most Web-based applications are ephemeral applications that users encounter as a by-product of their surfing. Even if users deliberately seek out a new app, they often approach it without a conceptual model of how it works. People don’t know the workflow or the steps, they don’t know the expected outcome, and they don’t know the basic concepts that they’ll be manipulating.
9. Not Indicating How Info Will Be Used
The worst instance of forcing users through a workflow without making the outcome clear is worth singling out as a separate mistake: Asking users to enter information without telling them what you’ll use it for.
A classic example is the “nickname” field in the registration process for a bulletin board application. Many users don’t realize the nickname will be used to identify them in their postings for the rest of eternity — so they often enter something inappropriate.
10. System-Centric Features
Too many applications expose their dirty laundry, offering features that reflect the system’s internal view of the data rather than users’ understanding of the problem space.
[Jackob Nielsen]
Written and submitted from Home, using my 802.11g WiFi network.
