You have five minutes while waiting for a friend to meet you for lunch, so you find yourself shopping for a new pair of shoes. When your friend arrives, you put the phone away, but leave the web page open to help you remember what you found when you get home.

While you’re at work, you read a restaurant review for a new place you think sounds tasty. Come dinnertime, you grab your phone to pull up the address and location.

One night on your tablet, you’re browsing articles for a report you’re writing at work. Back at your desk the next day, you struggle in vain to remember what you searched for to find those articles. Why can’t you find them again?

Sound familiar? If you’re like most people, it probably does. Research from Google (PDF) shows that 90 percent of people start a task using one device, then pick it up later on another device—most commonly, people start a task on smartphone, and then complete it on the desktop. As you might expect, people regularly do this kind of device switching for the most common activities, like browsing the internet (81 percent) or social networking (72 percent). Certain categories like retail (67 percent), financial services (46 percent), and travel (43 percent) also seem to support this kind of sequential use of different devices.

Dual-screen or multi-screen use of devices gets a lot of attention, but we tend to focus on simultaneous usage—say, using tablets or smartphones while watching TV. Publishers, advertisers, and social networks are all actively trying to figure out how to deliver a good experience to users as they shift their attention between two screens at the same time. Sequential usage is every bit as common, but we rarely acknowledge this behavior or try to optimize for this experience.

When people start a task on one device and then complete it on another, they don’t want different content or less content, tailored for the device. They want the same content, presented so they can find it, navigate it, and read it. They imagine that their devices are different-sized windows on the same content, not entirely different containers.

What should we do to provide a good experience for users who want to complete the same task across more than one device?

Content parity

Let’s make device-switching the final nail in the coffin for the argument that mobile websites should offer a subset of the content on the “real” website. Everyone’s had the frustrating experience of trying to find content they’ve seen on the desktop that isn’t accessible from a phone. But the reverse is also a problem: users who start a task from a smartphone during a bit of free time shouldn’t be cut off from options they’d find back at their desktop.

Consistent navigation labels

When picking up a task on a second device, about half of users say they navigate directly to the website to find the desired information again. Users who are trying to locate the same information across a mobile site (or app) and a desktop site can’t rely on the same visual and spatial cues to help them find what they’re looking for. As much as possible, make it easy for them by keeping navigation categories and hierarchy exactly the same. There aren’t that many cases where we truly need to provide different navigation options on mobile. Most desktop navigation systems have been extensively tested—we know those categories and labels work, so keep them consistent.

Consistent search

About 60 percent of users say they’d use search to continue a task on another device. Businesses wondering whether “mobile SEO” is necessary should keep in mind that user tasks and goals don’t necessarily change based on the device—in fact, it’s often the identical user searching for the exact information that very same day. It’s frustrating to get totally different results from different devices when you know what you’re looking for.

Handy tools

Users have taught themselves tricks to make their transition between devices go more smoothly—about half of users report that they send themselves a link. Sites that don’t offer consistent URLs are guaranteed to frustrate users, sending them off on a quest to figure out where that link lives. Responsive design would solve this problem, but so would tools that explicitly allow users to save their progress when logged in, or email a link to the desktop or mobile version of a page.

Improved analytics

Mobile analytics is still in the dark ages. Tracking users between devices is challenging—or impossible—which means businesses don’t have a clear picture of how this kind of multi-device usage is affecting their sales. While true multi-channel analytics may be a ways off, organizations can’t afford to ignore this behavior. Don’t wait for more data to “prove” that customers are moving between devices to complete a task. Customers are already doing it.

It’s time to stop imagining that smartphones, tablets, and desktops are containers that each hold their own content, optimized for a particular browsing or reading experience. Users don’t think of it that way. Instead, users imagine that each device is its own window onto the web.