What does it mean for a site to be SEO friendly? It goes beyond just posting quality content (though that’s a very important part!). There are all kinds of ways big and small that can prevent your site from being seen by search engines and thus by users. Our free audit tool begins by looking at some of the most important facets of your website you might not even be aware of.
Have you ever received a warning from Google Chrome to not visit a page? It will block the page and prevent you from going there because of some security issue. We begin by ensuring your website passes a SSL Certificate Validity Check. This a whole range of security protocols that should be within your website’s coding or built-in to the domain. It shows the world that your site is trustworthy!

You may not want certain pages of your site crawled because they might not be useful to users if found in a search engine's search results. If you do want to prevent search engines from crawling your pages, Google Search Console has a friendly robots.txt generator to help you create this file. Note that if your site uses subdomains and you wish to have certain pages not crawled on a particular subdomain, you'll have to create a separate robots.txt file for that subdomain. For more information on robots.txt, we suggest this Webmaster Help Center guide on using robots.txt files13.
SEM is a broader term than SEO, and is used to encompass different options available to use a search engine’s technology, including paid ads. SEM is often used to describe acts associated with researching, submitting and positioning a website within search engines.  It includes things such as search engine optimization, paid listings and other search-engine related services and functions that will increase exposure and traffic to your Web site. 
Optimizing a website may involve editing its content, adding content, and modifying HTML and associated coding to both increase its relevance to specific keywords and remove barriers to the indexing activities of search engines like Google ,Yahoo etc.[citation needed] Promoting a site to increase the number of backlinks, or inbound links, is another SEO tactic. By May 2015, mobile search had surpassed desktop search.[3]