What are classes? Class style rules are defined in the head element, CSS rules are between the style element, Classes are created to individualize styles, Each class begins with a period followed by the unique class name, Classes are applied to any xhtml, element or text block using div and span selectors, No programming terms can be use as class names, When applying the classes, the period is not used and the name is quoted.

What are Id's? IDs are defined in the head between the style elements, IDs begin with a pound sign (#) an a unique term, IDs are used only once on a page, Apply the ID term without the pound sign, Applied to any xhtml element, div or span elements, These special selectors allow JavaScript functions to manipulate objects defined with the pound sign.

How do you apply them to an html element? Classes will be used multiple times and id's will be used once.

How to redefine an html tag? Give the element a tag through the css.