applying css styles to documents.
style attribute: set directly on an html element in the style attribute
stylesheet rule selectors
tag name (element) selector: any element of the given type name
class (class attribute) selector: any element that has the given class
tag name + class (combination) selector: any element of the given type name that also has the given class
id (id attribute) selector: any element that has the given id
style sheet rule precedence
default style sheet is at the lowest
user style sheet overrides the default style sheet
the author style sheet overrides the user style sheet
unless rules in the user style sheet include the !important modifier