CSS style guides are a group of documents that outline the coding style, best practices, and visual design properties (e.g. colors, layout grid dimensions, etc.) of a site. The goal of having a style guide is to maintain consistency across a product.

Below is a sample list of CSS Style Guides available on the internet,

Airbnb CSS / Sass Styleguide

https://github.com/airbnb/css

Github Style Guide

https://styleguide.github.com/

Wordpress CSS Coding Standards

https://make.wordpress.org/core/handbook/best-practices/coding-standards/css/

Google HTML/CSS Style Guide

https://google.github.io/styleguide/htmlcssguide.html

Bootstrap CSS Code Guide

https://codeguide.co/#css

Lonley Planet CSS Code Guide

https://rizzo.lonelyplanet.com/documentation/css/naming

ThinkUp CSS Code Guide

https://github.com/ThinkUpLLC/ThinkUp/wiki/Code-Style-Guide:-CSS

Idiomatic CSS

https://github.com/necolas/idiomatic-css

CSS Guidlines

https://cssguidelin.es/

CSS Style Guide

https://www.smashingmagazine.com/2008/05/improving-code-readability-with-css-styleguides/

jQuery CSS Style Guide

https://contribute.jquery.org/style-guide/css/

BEM

http://getbem.com/introduction/

Atomic CSS

https://acss.io/

Object-Oriented CSS

http://oocss.org/

Suit CSS

https://suitcss.github.io/

SendGrid Style Guide

https://styleguide.sendgrid.com/

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