Separating form, content and function

In session 2 we looked at HTML, HTML is intended to be used to describe the content of a page, its structure, headings, paragraphs, lists etc - NOT its form, the way it looks.
The visual appearance or form of the page is supposed to be done using CSS - cascading style sheets. A well designed site uses common css files which allow the visual appearance of the whole site to be modified and updated very quickly - and to be repurposed for different applications, like print, mobile phones etc.
See the website http://www.csszengarden.com for an example of the power of css.
The final part of the equation is function - how you use a web site - discussion to come.
An excellent design marries all three, content with form and function.