Usability on the web, or user-centered design as it’s sometimes called, is important for the same reasons why usability is important in the real world. That is to say, it is best when it doesn’t call attention to itself and instead creates the conditions for successful interactions. By interactions I’m not necessarily referring to the point and click variety, but I’ll get to that.

Usability has been an issue within industrial design and architecture community for far longer than the web has even existed. This aspect of usability is concerned mainly with the organization of three-dimensional space and how humans interact with their physical environment. It could be as basic as the position of a light switch or the height of a cabinet. Or it could be somewhat more ambiguous.

Think of a time when you’ve pushed a door that’s meant to be pulled, or vice versa. You felt like an idiot, didn’t you? That feeling probably only lasted a moment, but it was real. An interaction that you’ve performed hundreds of times suddenly presented an unwelcome challenge. It called attention to itself, snapping you out of whatever reverie, conversation, or pursuit you may have otherwise been engaged in at the time.

So what happened? In a sense, your trust was violated. Your understanding was that the door was there to walk through and that assumption was challenged. This was not a contemporary art installation where you might have ruminated on that particular metaphysical question, this was a building. Your tacit understanding was that it should allow you relatively unfettered access or egress and it violated this understanding. Somehow the design failed to communicate how it worked.

In the real world you may not have a choice about whether or not to enter that building through the tricky door, but online even the smallest usability challenge can cause devastating results.  Once the usability fails the smell test, it’s not a stretch to imagine how a site could botch the credit card transaction, the shipping, the internal inventory, or something else.

In short, if the user’s experience on the site is clearly not a priority, it’s difficult to imagine what would be.  With that erosion of trust, a competitor’s site can start to look much more attractive.

The web is no longer a novelty, it is the medium through which we transmit and consume information on a daily basis. As such, we need to be able to perform the specific tasks to those ends as quickly, naturally, and efficiently as possible. Usability is just the word that we use to describe how to make that experience as painless, as easy, and as enjoyable as possible.