External style sheets.
• An external style sheet is a separate, text-only document that contains a number of style rules.
• It must be named with the .css suffix.
• The .css document is then linked to or imported into one or more HTML documents. • Embedded style sheets. • It is placed in a document using the style element, and its rules apply only to that document.
• The style element must be placed in the head of the document. This example also includes a comment