What is one of the most important things I should do to ensure my site or app is easy to use?

Your goal should be for each page or screen to be self-evident so that the average user will know what it is and how to use it just by looking at it. In other words, they'll "get it" without thinking about it.

Sometimes, though, you have to settle for self-explanatory if you're doing something original, groundbreaking, or inherently complicated. On a self-explanatory page, it takes a little thought to "get it". But only a little. The appearance of things (like size, colour, and layout), their well-chosen names, and the small amounts of carefully crafted text should all work together to create a sense of nearly effortless understanding.

Here's the rule: If you can't make something self-evident, you must at least make it self-explanatory.

Oddly enough, not for the reason people usually cite:

On the Internet, the competition is always just one click away, so if you frustrate users, they'll head somewhere else

There's indeed a lot of competition out there. Especially in things like mobile apps, where there are often many readily available (and equally attractive) alternatives, and the cost of changing horses is usually negligible (99 cents or even "Free").

But it's not always true that people are fickle. For instance:

They may have no choice but to stick with it if it's their only option (e.g., a company intranet, or their bank's mobile app, or the only site that sells the rattan they're looking for).

You'd be surprised at how long some people will tough it out on sites that frustrate them, often blaming themselves and not the site. There's also the

"I've waited ten minutes for this bus already, so I may as well hang in a little longer" phenomenon.

Besides, who's to say that the competition will be any less frustrating?

Making every page or screen self-evident is like having good lighting in a store: it just makes everything seem better. Using a site that doesn't make us think about unimportant things feels effortless, whereas puzzling over things that don't matter to us tends to sap our energy and enthusiasm-and time.

When we examine how we use the Web, the main reason why it's important not to make me think is that most people will spend far less time looking at the pages we design than we'd like to imagine.

As a result, if Web pages are going to be effective, they have to work most of their magic at a glance. And the best way to do this is to create pages that are self-evident or at least self-explanatory.