Search engines typically use a set of signals to determine how a website ranks for a particular keyword. These signals get their own values. The values are then given a weight and then based on the total score, pages are ranked for keywords and phrases. Google for example has stated that they use in the region of a hundred or more ranking signals. Here are few of the more well known ranking signals.
Site speed – This is a scoring of how quickly your site loads. Through this, larger bloated sites are penalized and smaller quicker to load sites get a boost. For a short time Google themselves hosted a site caching service for free.
Aesthetics – A machine learning algorithm determines a score for how good your site looks. This scoring was based on how hundreds of people graded various websites they came across. Using those scores as a template, Google’s machine learning AI can score website design.
Link graph – Inbound links and anchor texts were the secret sauce in Google’s original search algorithm. Now this same link graph is calculated several times over. Now in addition the score of the site linking and the anchor text, other words on the same page are also considered signals.
Other ranking signals such as title, description and keyword density are no longer as heavily weighted as they used to be. These are all being gradually replaced by social and other factors.