Although more and more keywords are getting encrypted by Google every day, another smart way to come up with keyword ideas is to figure out which keywords your website is already getting found for. To do this, you'll need website analytics software like Google Analytics or HubSpot's Sources report, available in the Traffic Analytics tool. Drill down into your website's traffic sources, and sift through your organic search traffic bucket to identify the keywords people are using to arrive at your site.
Being ‘relevant’ comes down to keywords & key phrases – in domain names, URLs, Title Elements, the number of times they are repeated in text on the page, text in image alt tags, rich markup and importantly in keyword links to the page in question. If you are relying on manipulating hidden elements on a page to do well in Google, you’ll probably trigger spam filters. If it is ‘hidden’ in on-page elements – beware relying on it too much to improve your rankings.
QUOTE: The manual actions team… can look at the labels on the on the links or a site gets. Basically, we have tons of link labels; for example, it’s a footer link, basically, that has a lot lower value than an in-content link. Then another label would be a Penguin real-time label. If they see that most of the links are Penguin real-time labelled, then they might actually take a deeper look and see what the content owner is trying to do.” Gary Illyes, Google 2016
Advertising with Google won't have any effect on your site's presence in our search results. Google never accepts money to include or rank sites in our search results, and it costs nothing to appear in our organic search results. Free resources such as Search Console, the official Webmaster Central blog, and our discussion forum can provide you with a great deal of information about how to optimize your site for organic search.