Website Anatomy
Website Document Flow
Not many designers will tell you about correct document flow as it's pretty difficult to implement.
If you have a look at the diagrams on the website anatomy page you may notice in the first diagram that the column order reads Column 2, Column 1 then Column 3. This is not a mistake! Column 1 is the main information column and the other side columns are for links and extra information. When a search engine reads the document we want the important information in the main column to be read first and to be given the highest priority. If you are using Firefox you can use the alternate CSS styles we have set up on this site to display the actual document flow (or just use the view page source option to see the raw code).
Table base Layout - NO!
Positioning using tables is much easier for lazy developers and I have to confess that I have had to use this technique in the past, but from November 2007, no Hardington developed websites will use tables for layout. Tables are for tabular data and must be correctly styled using summaries for visually impaired users (and search engines), and correctly styled using CSS Style sheets. The page on Google Keywords has some examples of tabular data.
Why is using tables for layout such a bad thing? The main problem is that the document changes from a semantic reusable document into a document that has been internally styled. If you can imagine a tiny PDA screen trying to display this page, the data in the right hand column would not be shown. The document would not be printed correctly if the user set a page size smaller than the base document size, search engines would read the information in the wrong order.
Nice CSS based Layout
We layout the web page documents using logical document flow - The header at the top, the columns of data in the order of importance, then lastly stuff like navigation menus - nice!
Here is a nice page explaining all about semantic web design - The Motive Glossary web design site.