Since heading tags typically make text contained in them larger than normal text on the page, this is a visual cue to users that this text is important and could help them understand something about the type of content underneath the heading text. Multiple heading sizes used in order create a hierarchical structure for your content, making it easier for users to navigate through your document.
#16 is interesting because no one really knows about it. Myself and a former colleagu did a test on it about 4 years ago and published our results which conculded what you are saying. Since then I’ve been careful to follow this rule. The only issue is that often times using the exact kw does not “work” for navigation anchor texts. But with a little CSS trickery one can get the code for the nav bar to be lower in the code, prioritizing contextual links. I’ve also seen sites add links to 3-5 specific and important internal pages with keyword rich anchor texts, at the very top of the page in order to get those important internal links to be indexed first.
Some search engines have also reached out to the SEO industry, and are frequent sponsors and guests at SEO conferences, webchats, and seminars. Major search engines provide information and guidelines to help with website optimization. Google has a Sitemaps program to help webmasters learn if Google is having any problems indexing their website and also provides data on Google traffic to the website. Bing Webmaster Tools provides a way for webmasters to submit a sitemap and web feeds, allows users to determine the "crawl rate", and track the web pages index status.
Companies that employ overly aggressive techniques can get their client websites banned from the search results. In 2005, the Wall Street Journal reported on a company, Traffic Power, which allegedly used high-risk techniques and failed to disclose those risks to its clients. Wired magazine reported that the same company sued blogger and SEO Aaron Wall for writing about the ban. Google's Matt Cutts later confirmed that Google did in fact ban Traffic Power and some of its clients.
Expert roundups have been abused in the Internet Marketing industry, but they are effective for several reasons. First, you don’t have to create any content. The “experts” create all the content. Second, it is ego bait. Meaning, anyone who participated in the roundup will likely share it with their audience. Last, it is a great way to build relationships with influencers.
While short-tail keywords are often searched more frequently, it is more difficult to rank for them on search engines. Targeting long-tail keywords, on the other hand, gives you a better chance of ranking higher (even on the first page) for queries specific to your products and services—and higher ranking means more traffic. Plus, as search engines and voice-to-text capabilities advance, people are using more specific phrases to search online. There are many free tools available to help you find keywords to target, such as Answer the Public.
The world is mobile today. Most people are searching on Google using a mobile device. The desktop version of a site might be difficult to view and use on a mobile device. As a result, having a mobile ready site is critical to your online presence. In fact, starting in late 2016, Google has begun experiments to primarily use the mobile version of a site's content42 for ranking, parsing structured data, and generating snippets.
Search engines use complex mathematical algorithms to interpret which websites a user seeks. In this diagram, if each bubble represents a website, programs sometimes called spiders examine which sites link to which other sites, with arrows representing these links. Websites getting more inbound links, or stronger links, are presumed to be more important and what the user is searching for. In this example, since website B is the recipient of numerous inbound links, it ranks more highly in a web search. And the links "carry through", such that website C, even though it only has one inbound link, has an inbound link from a highly popular site (B) while site E does not. Note: Percentages are rounded.