QUOTE: “If an off-domain link is made by an anonymous or unauthenticated user, I’d use nofollow on that link. Once a user has done a certain number of posts/edits, or has been around for long enough to build up trust, then those nofollows could be removed and the links could be trusted. Anytime you have a user that you’d trust, there’s no need to use nofollow links.” Matt Cutts, Google 2006

Robots.txt is not an appropriate or effective way of blocking sensitive or confidential material. It only instructs well-behaved crawlers that the pages are not for them, but it does not prevent your server from delivering those pages to a browser that requests them. One reason is that search engines could still reference the URLs you block (showing just the URL, no title or snippet) if there happen to be links to those URLs somewhere on the Internet (like referrer logs). Also, non-compliant or rogue search engines that don't acknowledge the Robots Exclusion Standard could disobey the instructions of your robots.txt. Finally, a curious user could examine the directories or subdirectories in your robots.txt file and guess the URL of the content that you don't want seen.
Redirecting is the act of sending a user to a different URL than the one initially requested. There are many good reasons to redirect from one URL to another, for example, when a website moves to a new address. However, some redirects are designed to deceive search engines and users. These are a very poor user experience, and users may feel tricked or confused. We will call these “sneaky redirects.” Sneaky redirects are deceptive and should be rated Lowest.
This relationship between rankings and clicks (and traffic) is strongest amongst the top 3 search results. However, changing layout of the search results pages is constantly changing, with the inclusion of Google’s Knowledge Graph data and the integration of Universal Search elements (SERP Features) like videos, maps and Google Shopping ads. These developments can mean that the top 3 organic rankings are no longer the 3 best positions on the SERP. This has been demonstrated in heatmap and eye-tracking tests.
If you have a commenting system (like Drupal, Joomla or WordPress) that allows for search engine friendly links (commonly called dofollow links) from your blog or site, you will probably, eventually be the target of lots of spam, be complicated in tiered link schemes and potentially fall foul of Google’s webmaster guidelines on using the attribute in certain situations.
The higher the search volume for a given keyword or keyword phrase, the more work is typically required to achieve higher rankings. This is often referred to as keyword difficulty and occasionally incorporates SERP features; for example, if many SERP features (like featured snippets, knowledge graph, carousels, etc) are clogging up a keyword’s result page, difficulty will increase. Big brands often take up the top 10 results for high-volume keywords, so if you’re just starting out on the web and going after the same keywords, the uphill battle for ranking can take years of effort.

While most of the links to your site will be added gradually, as people discover your content through search or other ways and link to it, Google understands that you'd like to let others know about the hard work you've put into your content. Effectively promoting your new content will lead to faster discovery by those who are interested in the same subject. As with most points covered in this document, taking these recommendations to an extreme could actually harm the reputation of your site.
Online reviews have become one of the most important components in purchasing decisions by consumers in North America. According to a survey conducted by Dimensional Research which included over 1000 participants, 90% of respondents said that positive online reviews influenced their buying decisions and 94% will use a business with at least four stars. Interestingly, negative reviews typically came from online review sites whereas Facebook was the main source of positive reviews. Forrester Research predicts that by 2020, 42% of in-store sales will be from customers who are influenced by web product research.

There are a lot of definitions of SEO (spelled Search engine optimisation in the UK, Australia and New Zealand, or search engine optimization in the United States and Canada) but organic SEO in 2020 is still mostly about getting free traffic from Google, the most popular search engine in the world (and almost the only game in town in the UK in 2020):
However, we do expect websites of large companies and organizations to put a great deal of effort into creating a good user experience on their website, including having helpful SC. For large websites, SC may be one of the primary ways that users explore the website and find MC, and a lack of helpful SC on large websites with a lot of content may be a reason for a Low rating.
Structured data21 is code that you can add to your sites' pages to describe your content to search engines, so they can better understand what's on your pages. Search engines can use this understanding to display your content in useful (and eye-catching!) ways in search results. That, in turn, can help you attract just the right kind of customers for your business.
The SEO starter guide describes much of what your SEO will do for you. Although you don't need to know this guide well yourself if you're hiring a professional to do the work for you, it is useful to be familiar with these techniques, so that you can be aware if an SEO wants to use a technique that is not recommended or, worse, strongly discouraged.