The structure is the html, presentation: css, behavior: javascript. in 1996 css, html, and javascript were all mixed togeather throughout the code but now they are all seperate and organized it all changed in 2005 it was called ajax (dynamic html) when it is organized it will make it easier to make better non buggy web pages. an escalator can never break: it can only become stairs. just like your web page if you make it right. html defines content and structure html is a formating language not a programming language. right html first then css. three ways of putting css on a web page. inline embeded and external. there is three parts to css there is the selector, the properties, and the values. there is four ways to select in css, you have element, class, id, and position in the document.