the latest version(current) of the css specification is CSS3. NOT ALL of the
[WHY]
] seperation of concerns - presentation
] maintainablity -
] manageability - change the color/alignment/size of all heading h1 elements on all pages on the entire site with one change/edit in one file VERSUS changing it on each h1 element on each page within the entire site
[WHERE]
] any web site where you have more than 1 page or even on a single page when there is /may be multiple elements that share the same attributes.
[WHEN]
]
[EXAMPLE]
]
[HOW-TO]
define style rules/classes/properties in a style class, typically stored in a seperate .css file which the calling document links to
apply the defined "style" class to the desired html element,