"Cascading Style Sheets (abbreviated CSS) add a new dimension to our pallet of Web design tools. They have the potential to allow a webmaster to control the appearance of countless web pages with one single file.
This file, known as a "Style Sheet", can be referenced by any number of web pages to define how certain areas of text appear on those pages.
With a simple change to this style sheet (to the font face, color, size, highlighting, border, or other properties), any page in the entire web site can instantly and easily be altered, eliminating the need to go through and change every single HTML tag.
In addition, style sheets add a number of other features, such as being able to specify text size in terms of points, highlighting text, using borders without the hassle of tables, defining paragraph indents, margins, and object positioning. They even provide the ability to layer elements over one another!"