From error to error one discovers the entire truth. Sigmund Freud

In my last posting (Usability Basics: Keep the User Informed) I talked about how the interaction with other humans differ from interactions online because of something called a feedback loop- the ability we have of constantly assessing the verbal and non-verbal communication that is happening.

Helping a user prevent errors is another way of closing that feedback loop online to create usable sites. In the physical world we come up against real boundaries that signal to us about potential problems. I don’t need messaging on the side of an eight ounce glass telling me not to put more than 8 ounces in it, otherwise I’ll have a mess- I can see how much the glass will hold. Online we’re not always privvy to such physical cues, in which case we do need assistance via messages, instant feedback, or imposed limits in order to avoid problems.

One of the most visible ways this usability principle is applied online is with creating passwords. How many times have we created a password, only to be presented with an error telling us that we didn’t do it right. Oh, you forgot to include a number, or capital letter. Preventing errors is all about being upfront with users and giving them (us!) the information we need to avoid extra clicks, extra time, more page reloads, etc. Let’s look at Drupal 6. This version uses messages to help me prevent making an error when creating a password. The site checks the password on the fly, telling us how many characters we must use, recommendations on the types of characters to use, as well as providing a “strength” meter to show us how well we’ve done before we submit the form for procesing. Nice.

Another way sites are endeavoring to help prevent errors is through the use of Ajax to validate field values and provide instant feedback. Kayak.com does a good job of helping users prevent errors. When searching for a flight I begin typing in the name of a city and the site returns a list of potential matches. This actually satisfies two usability principles- helping me to prevent errors by displaying only valid city names and ; and it relieves me from having to remember the three letter airport identifier. Good job.

Using imposed limits to help avoid errors is very common when selecting calendar dates. The Wachovia website uses text fields with the proper date format listed below the field. This is better than not having any format information, but I can still enter an improper date and submit the form. A better solution is to force the user to select a date from either a drop down list or via a calendar widget. This ensure the date is entered correctly the first time and helps the user avoid making an error.

Helping prevent errors is communicating to your site visitors about rules they must follow, boundaries they must operate within, and values that are expected to ensure they can keep moving forward. This is one important piece of creating usable websites, designing positive interactions, and keeping processes as transparent as possible.

This entry was posted on Thursday, October 2nd, 2008 at 1:04 pm and is filed under Usability. You can follow any responses to this entry through the RSS 2.0 feed. You can leave a response, or trackback from your own site.