Google shaking up search recommendations on smartphones

The revised formula, scheduled to be released Tuesday, will favor websites that Google defines as "mobile-friendly." Websites that don't fit the description will be demoted in Google's search results on smartphones while those meeting the criteria will be more likely to appear at the top of the rankings — a prized position that can translate into more visitors and money.

Although Google's new formula won't affect searches on desktop and laptop computers, it will have a huge influence on how and where people spend their money, given that more people are relying on their smartphones to compare products in stores and look for restaurants. That's why Google's new rating system is being billed by some search experts as "Mobile-geddon."

"Some sites are going to be in for a big surprise when they find a drastic change in the amount of people visiting them from mobile devices," said Itai Sadan, CEO of website-building service Duda.

It's probably the most significant change that Google Inc. has ever made to its mobile search rankings, according to Matt McGee, editor-in-chief for Search Engine Land, a trade publication that follows every tweak that the company makes to its closely guarded algorithms.

Here are a few things to know about what's happening and why Google is doing it.