W3C is The World Wide Web Consortium
W3C introduce a set of standards , primarily pursues its mission through the creation of Web standards and guidelines designed to ensure long-term growth for the Web. So all search engines encourage webmasters to adhere those standers.
When we create a html page , we can validate and see [...]

Page size is a key factor in SEO. Because the page loading speed depends on the page size.
A page with many images and multimedia stuff slows down the site. That will affect the site response time.
Always try to keep lass that 100k page size. If your page size is too large, break it to two [...]

Meta tags are a main factor in SEO.This targets only crawlers. Human visitors can’t see meta tags unless view source of the HTML. There are different types of html meta tags.
Most important meta tags are
Keyword meta tag – Use less than 10 words .All the word in this tag MUST appear somewhere in the body [...]