CSS is an abbreviation for the term "Cascading Style Sheets". CSS was first developed in 1997 as a way to separate the way a Web page looked from the content and behavior. CSS defines how to display the content contained in markup and is stored in style sheets.
In CSS the cascade is like a waterfall, as the user agent encounters style rules it applies them one after the other. The order of styles is:
- browser defaults
- external style sheets
- internal style sheets
- inline styles
- the more specific style selector will take precedence
- h2 is more specific than the universal selector
- h2.class is more specific than h2
- h2.id is more specific than h2.class
CSS was generated to separate the look and feel or style of Web pages from the XHTML markup or structure of the pages.
There are three ways you can add styles to your Web pages:
- inline styles
- embedded styles
- external styles
Some people use a CSS style sheet editor.
But it's easy to edit a style sheet using just a text editor.

