Simplest tip ever: Use Visual Studio's Go To Definition with CSS classes to get from your HTML to the relevant CSS rule. First click on the name of a class in your HTML: ...

Dabblet's focus on HTML and CSS makes it an excellent tool for beginners and anyone curious about the latest HTML5 tags and CSS3 styles.

Google’s Search Relations team explains how CSS affects SEO, addressing myths about class names, pseudo elements, and page performance.