A style sheet is a free-flowing document that can either be referenced by, or included into a HTML document. Style sheets use blocks of formatted code to define styles for existing HTML elements, or new styles, called classes.

Style sheets can be used by Professional website design to change the height of some text, to change the background color of a page, to set the default border color of a table…the list goes on and on. Put simply though, style sheets are used to set the formatting, color scheme and style of an HTML page.

Style sheets should be used instead of the standard <font>,, and <u> tags because:

- One style sheet can be referenced from many pages, meaning that each file is kept to a minimum size and only requires only extra line to load the external style sheet file

- If you ever need to change any part of your sites look/feel, it can be done quickly and only needs to be done in one place: the style sheet.

- With cascading style sheets, there are many, many page attributes that simply cannot be set without them: individual tags can have different background colors, borders, indents, shadows, etc.