Cascading Style Sheets
Cascading style sheets are not meant to replace html but to compliment it. CSS gives an author a way to keep everything the same without constant change or multiple repetetion of code.
Css has become an industry standard from the w3c as a way of consitencey. It also is the preffered way of site layout instead of tables, even though table layout will be around for some time because of cross browsr compatibility.