http://www.w3.org/TR/CSS21/cascade.html#inheritance
http://www.w3.org/TR/CSS21/cascade.html#cascade
http://www.w3.org/TR/CSS21/cascade.html#specificity
http://www.w3.org/TR/CSS21/cascade.html#inheritance
http://www.w3.org/TR/CSS21/cascade.html#cascade
http://www.w3.org/TR/CSS21/cascade.html#specificity