Google just made a huge update that could affect millions of businesses. Here's what you need to know

The day of reckoning has arrived.

Today, Google is making a major update to its mobile search algorithm that will change the order in which websites are ranked when users search for something from their phone.

The algorithm will start $4 - ones with large text, easy-to-click links, or that resize to fit whatever screen they're viewed on - and ranking them higher in search. Websites that aren't mobile-friendly will get demoted.

This change could be apocalyptic for millions of websites, which could find that they've lost their coveted ranking, so it has $4"

More than 45% of Fortune 500 companies and 29% of Internet Retailer 500 sites weren't mobile friendly by early April, only weeks ahead of the update, according to research from digital marketing agency RKG Merkle.

Small businesses are generally seen at greater risk of being affected by the change, though, because they have a higher likelihood of not knowing about the update, or not having the time or resources to make changes, Itai Sadan, CEO of $4, told Business Insider. Several small businesses told Business Insider that $4, for example, though some already had mobile-friendly websites.

Google first $4, giving webmasters nearly two months to make the changes necessary to keep their sites from disappearing from mobile search results, as well as $4 (and see why not, if they aren't).

Now that the update has started rolling out, here are 4 important things you need to know:

• Every website should be mobile friendly, even if most of their traffic comes from desktop. The update doesn't apply to tablets or desktop, just smartphones, but everyone should make their site mobile friendly, because about 60% of search traffic now comes from mobile. "Statistics show that more people are going 'mobile only' - either because they never had a desktop or because they won't replace their existing desktop," $4"Additionally, a non-mobile-friendly site may not see many mobile visitors precisely for that reason.
• We won't be able to determine which sites' rankings have been affected for a week or so. Although the update rolls out today, it takes about a week for Google's update to $4.
• Run a website but didn't make the deadline? Don't worry. If a website isn't mobile-friendly by today, webmasters can quickly make changes, $4, and then expedite how fast Google re-crawls their pages by using $4 in $4.
• Really good websites won't totally disappear if they're not mobile friendly. Although the update will punish sites that don't look work well on smartphones, the content of a website is still very important. "The intent of the search query is still a very strong signal," $4, "So even if a page with high quality content is not mobile-friendly, it could still rank high if it has great content for the query."