Some user agents allow users to navigate among table cells and access header and other table cell information. Unless marked-up properly, these tables will not provide user agents with the appropriate information. (Refer also to guideline 3.)
There are two ways a non-graphical browser can handle a table. The old way was to simply ignore them. Lynx uses this method. The big problem with tables and these browsers is that with the "old nav bar down the left side of the screen" design the user has to listen to a repetitive list of links at the top of every page in your site. One solution is to put the links down the right side. Another is to use a "skip navigation" link.
But TABLEs are a legitimate HTML element in their own right. There how you organize tabular data and screen readers need to be able to present the data in a way that the user can understand the relationships. And the advanced screen readers do have a way. Essentially they call out the contents of the appropriate header cell or cells with each data cell. And if you haven't indicated what the header cells are then the browser just guesses. If you have used tables for layout then this will really make a mess out of your page. In other words, "this may present problems when rendering to non-visual media."
“The power of the Web is in its universality. Access by everyone regardless of disability is an essential aspect.”
—Tim Berners-Lee, W3C Director and inventor of the World Wide Web
In the first example, not only is the page totally terrible (on the inside), but it is difficult to code and takes longer to load (rhyme). The logo has three TDs the consist of parts of the logo, and then there is two other cells that contain the navigation and content. In the second example, however, there is a simple image which is the logo, a DIV holds images for navigation, and a seperate DIV contains the content. Here is the source code for the second example (note: I have not validated the CSS code, but it should be valid):
Here, you see that the #nav sets the CSS properties for the <DIV ID="nav"> division. The same applies with the rest of the DIVs. Other CSS code is simply for page-look (body, img, etc.). You may want to take a look at the documentation on CSS (see CSS 2 Ref link below), or some other neat things you can do with CSS (see CSS ZendGarden link below).