Meta tags. Meta tags still play a vital role in SEO. If you type any keyword into a search engine, you’ll see how that keyword is reflected in the title for that page. Google looks at your page title as a signal of relevance for that keyword. The same holds true for the description of that page. (Don't worry about the keyword title tag -- Google has publicly said that it doesn't pay attention to that tag, since it has been abused by webmasters and all those trying to rank for certain keywords.)
A navigational page is a simple page on your site that displays the structure of your website, and usually consists of a hierarchical listing of the pages on your site. Visitors may visit this page if they are having problems finding pages on your site. While search engines will also visit this page, getting good crawl coverage of the pages on your site, it's mainly aimed at human visitors.
Great content. Although I disagree with ‘the best times to post’ section. It is important to understand your audience. For example, if your brand/business is in high school, there will be low engagement until 2-5 when they are out of school. I highly suggest using instagram analytics (a subsidiary of facebook analytics) which gives you all of the details on when your followers are active. https://www.facebook.com/help/788388387972460
For some reason I had to delete some pages, these pages are using the HTML suffix, so I blocked them in robots.txt use Disallow: /*.html, but it’s been almost a year, I found that google robot often capture these pages, How can I quickly let Google completely remove these pages? And I have removed these URL from google webmaster tool by google index-> remove URLs, but Google still capture these pages.
If you are using Responsive Web Design, use meta name="viewport" tag to tell the browser how to adjust the content. If you use Dynamic Serving, use the Vary HTTP header to signal your changes depending on the user-agent. If you are using separate URLs, signal the relationship between two URLs by tag with rel="canonical" and rel="alternate" elements.