To understand this instructable, you'll need to know basic html and css. If you don't understand something, feel free to ask.
My personal homepage also uses this kind of div structure.
Step 1: Create the basic files
html file now contains:
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml" xml:lang="en" lang="en">
<link rel="stylesheet" href="style.css">
Save your html file as something.html. You can choose the name yourself. Your css file has to be saved as .css. Make sure you give it the same name as mentioned in the html file. In this case "style.css".
We now have a plain empty html page when previewed in our browser.