SEO - HTML - LAYOUT
I mentioned using this great tool: The Delorie.com Online LYNX Viewer Tool. This will help you compare one HTML page against another for it's layout's effectiveness at search engines.
Websites that rely heavily on graphical look and flash presentations, often suffer at the search engines. Here are some cool links to articles describing website layouts that create high performance search engine friendly sites:
The Table Trick
The table is trick is a strong HTML search engine optimization tehnique. Quoted directly from the site: "Table-based layout usually works well with search engines. However, a traditional design that contains the menu on the left and the content on the right does have one downside. In many cases, such a layout will cause your navigation menu to appear above your content in the source code. This is unlikely to create any major problems, but might make it slightly harder for your pages to obtain good rankings. Correcting this issue seems relatively simple, at least at first. It can be done by making some minor changes to the way your tables are arranged. The procedure is widely known in SEO circles as 'The Table Trick'".
This site assumes some basic HTML skill. Here, in essence is the "Table Trick":
<!-- Spacer Gif located in upper-left cell -->
<td><img src="/images/spacer.gif" width="1" height="1" alt=""></td>
<!-- main content cell first, with rowspan=2 -->
<td valign="top" align="left" rowspan="2">
... Put your main Content Here...
<td valign="top" align="left" width="25%">
... Put your Navigation Bar here...
Search Engine Optimized CSS layout
While there is still a lot of argument for and against the use of strict XHTML, one can definately benefit by making sure their choices in table layout or CSS are search engine friendly. I personally think that either is OK. Tables may still be stronger, and offer more platform compatibility - but XHTML strict positioning is a possible way of the future. Here is a great site regarding Search Engine Friendly Layout.
3 Column CSS Search Engine Friendly Layout
This page contains what many consider the "The Holy Grail" of layout. It offers the best of both worlds: 3 column layout, CSS positioning, and search engine optimization. Though it may produce trouble in some browsers, most will see exactly what you intend to present! Be sure to check that one out!
Added (Feb 2006):
Another fantastic, open licensed layout: