HTML CSS guidelines and best practices

[shantu]

• https://google.github.io/styleguide/htmlcssguide.html
• https://github.com/necolas/idiomatic-css
• https://csswizardry.com/2012/04/my-html-css-coding-style/
• http://codeguide.co/
• http://www.louddog.com/2008/create-maintainable-code-with-a-css-styleguide/
• https://www.smashingmagazine.com/2008/05/improving-code-readability-with-css-styleguides/