One button is a constant across the Web.
On the Web and mobile apps, user behavior is constantly evolving - the messy result of a complex and unpredictable calculus involving expectations, experience, technology, brands and a hundred other factors. Unless you're replicating an existing, proven Web site note-for-note and down to the last pixel, it's very difficult to predict how users will behave. After well over a decade of Web designers working to define "best practices," there's almost nothing we know for certain about what users will do.
Except for this: Users will always click on the back button.
The back button is the one unassailable, reliable element in Web design that every user knows and employs. It is the immediate, instinctive refuge for anyone who is confused. It will always take you back to the last point of familiarity and provide a stable return path as you explore new avenues - a lifeline to normalcy when something strange, disorienting (or even offensive) pops up unbidden.
Try to imagine the Web without it. Try to imagine a day without it. You can't.
It's no accident that the back button is built into every Web browser. Nor is it an accident that so many mobile apps replicate the back button within their own designs. It's one thing every user knows and trusts.
And this speaks volumes about how incomplete our toolbox is for constructing truly intuitive Web experiences.
Jump into any automobile and you'll find a steering wheel, gearshift, gas and brake pedals that all work the same and are placed exactly where you'd expect them, regardless of how vintage or novel the design of the car. Even the glove compartment is located in the same place, whether on a new Toyota or a vintage Chevy.
But with any given Web site, the only thing we can really know about how it works is that its links will take us somewhere and the back button will get us back.
That has enormous implications for anyone creating online media. When the only truly reliable interface element is outside of our purview - built into the browser itself - designers are obliged to try and supplement it with their own reliable cues: home buttons, search boxes, navigation bars and link types that behave as consistently and with as much order and logic as possible. At the same time, we want to keep our users returning, moving forward and looking at more of our Web sites, more of our mobile applications.
A million approaches, a million best practices, and yet one consistent, almost sacred rule: The user can always take a step back. That's the true nature of interactivity.