CSS

CSS is actually part of the HTML 4.0 specification. CSS stands for Cascading Style Sheets. It can be quite useful as it allows you to update your web page. For example, if you decide to change the font type of your web page to “Black Chancery” from “Times New Roman”, you would have to change the type in all the  tags in the source code. With CSS, you can define the fonts of your web page in a separate file and if you wish to change the font, you would merely have to change it once in the CSS file. This is only one of the uses of CSS. The disadvantage of CSS is that it is not compatible with some older browsers and is also not completely compatible with somewhat newer ones.

CSS can be used in an HTML document in three ways:

1. 1. Inline style sheet :  The style elements are added directly to the HTML tag.
2. 2. Internal style sheet: The style elements are incuded in the head section of the HTML document.
3. 3. External style sheet: The style elements are saved in a separate file (CSS file). This is useful and popular because it separates the actual content of the webpage from the presentation layout.

Courtesy by:
A Complete Introduction to the World of Web Design: A Visual Approach