Introduction to CSS

How it Works 

    
A style is a definition of fonts, colors, margin, layout etc.
    
Each style has a unique name called selector.
    
The selectors and their styles are defined in one place.
    
In your HTML contents you simply denote to the selectors whenever you want  to activate a certain style.

Merits of CSS

    
You can set the look of pages in one place instead than repeating yourself  over and over again throughout your site.
    
You can easily change the design of your web pages even after they're  created. Because styles are defined in one place you can change the look of the  entire site at once.
    
You can define font sizes and similar attributes with the same accuracy as  you have with a word processor.
    
You can set positions of the content with pixel exactness.
    
You can redefine entire HTML tags.
    
You can define customized styles for links.
    
You can define layers that can be positioned on top of each other.
    
Your pages will execute faster, since they aren't filled with tags that  define the look. The style definitions are kept in a single CSS document that is  only loaded once when a visitor enters your site.

Demerits of CSS

    
There is only one demerits of CSS, It will be work on only version 4  browsers or above.