By mid-2016, according to Google, 60 percent of searches came from smartphones. With that in mind, the search giant’s page-rank algorithm began giving serious weight to mobile-friendly sites. As Google constantly refines the algorithm to reflect changes it perceives in user behavior, expect mobile-optimization to increase in weight going forward.

Although most adult websites have been mobile-optimized for quite some time, it never hurts to take a look at how Google views the web today, not last week.

First, bear in mind Google does not consider all mobile devices equal. In Google-speak, “mobile” is synonymous with “smartphone.” Typically, the devices run on Android, iOS or Windows Phone operating systems and employ browsers that can do almost anything a desktop browser does. The difference between mobile devices and desktops is screen orientation (vertical vs. horizontal) and size.

Google does not consider tablets mobile devices. Because tablets possess larger screens than smartphones, users typically expect to see a website on a tablet look exactly like it does on a desktop computer, except smaller.

At the moment, here is Google’s best overarching advice for ensuring Google appreciates all the hard work you’ve done to make your website(s) mobile-friendly:

Signal to Google when a page is formatted for mobile (or has an equivalent page that’s formatted for mobile). This helps Google accurately serve mobile searchers your content in search results.

Keep resources crawlable. Do not use robots.txt to block search engines from accessing critical files on your site that help render the page (including ads). If Googlebot doesn’t have access to a page’s resources, such as CSS, JavaScript, or images, we may not detect that it’s built to display and work well on a mobile browser. In other words, we may not detect that the page is “mobile-friendly,” and therefore not properly serve it to mobile searchers.

Avoid common mistakes that frustrate mobile visitors, such as featuring unplayable videos (e.g., Flash video as the page’s significant content). Mobile pages that provide a poor searcher experience can be demoted in rankings or displayed with a warning in mobile search results.

Among the most common mistakes Google sees are:

Robots.txt files that prevent Googlebot from indexing assets like JavaScript, cascading style sheets and image files.

Unrecognizable or uncrawlable redirects from desktop to mobile sites (when the two are separate).

Faulty redirects and irrelevant crosslinks between desktop and mobile sites. The faulty redirect Google most often sees is a specific page on a desktop site redirects to the mobile site’s homepage. Any redirect that does not land a surfer exactly where he expected to be is heavily penalized by the search algorithm.

Videos or other content that are not playable because they are license-constrained or require a technology not supported on all mobile devices — Flash, for example. Google suggests using HTML5 where possible.

Mobile-only 404 pages. If, for some reason, a page on a responsive desktop site won’t render correctly on a mobile device, create a special mobile-friendly version and ensure mobile users are redirected there. Little irks Google more than 404 pages.

Interstitials or overlays, including ones that urge users to download a native app. This is a biggie. Google hates anything that comes between a mobile surfer and what he’s trying to view. Use unobtrusive banners or figure out some other way to get your promotional message across unless you enjoy being sent to the corner like a misbehaving schoolboy.

Failure to use the viewport meta-tag that tells browsers how to scale pages to suit the device on which they are being viewed.

Small font sizes that don’t scale with the viewport.

Touch elements that are too close to one another, making it difficult for users to tap the link they’re trying to tap.

Curious about how your site stacks up against Google’s ideal mobile-friendly destination? Google has provided a handy-dandy Mobile-Friendly Test for just that purpose.