How to Tell if a Website Is Built With CSS. One of the best ways to learn to build compelling business websites is to study the code that others create. While HTML is great for placing objects on ...

For instance, if a class defines a width of 100 pixels, all DIVS referencing that class will be 100 pixels wide. You can override a DIV's CSS class definition by updating the DIV's HTML code.

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