Cascading Style Sheets (CSS) can be used to style web pages. While HTML tells the browser what to display on a page, CSS tells the browser how to display it. CSS rules can be added to already existing HTML files or can be stored in separate .CSS files and linked to a webpage.
A CSS rule set consists of:
The selector points to the HTML element you want to style. In the case above the style will be applied to a heading.
The declaration block contains one or more declarations. These are separated by semicolons. Each declaration includes a property name and a value, separated by a colon, and the entire group of declarations is surrounded by curly brackets. Sometimes the declarations are shown on separate lines, so the same rule could appear as:
In either form, the heading would show on screen as blue text with a font size of 12.