Let's begin with the benefits of a tableless layout. These are only in the order that I feel they should go in, some things are more important to other people, so rank them as you will.

Forces You To Write Well-Formed Code

You cannot have a properly made tableless layout, and use improper and non-standard code. Well, let me correct that - you can (technically you can do it) but it defeats the whole purpose. When you are creating a tableless design, you should be using standards compliant code. I think that anything that makes you get into the habit of always writing clean code is a good thing.

Faster Loading Time

This is absolutely a benefit of a tableless layout, and for several reasons. First, on a fundamental level - tables load slowly. For the most part, unless you set the height and width of your table elements, all the text has to be loaded and rendered BEFORE the table sizes itself to the page. Of course, this is what so many people loved about tables isn't it? The fact that they were so easily sizeable. The downside is how much more time they take to load.

Okay, so the solution to that loading time is to set all the values explicitly, right? So now we see another downside. Code clutter that increases loading time. First of all, just by themselves, tables take allot of code. How many td open and close tags does your average table based layout have? Tons. Having to set all the values explicitly only adds to the page size and loading time.

Easier to Read Code

If you are using standard code, semantic document conventions, and a tableless layout, your code can be so clean that it looks practically like just regular text with a few extra symbols.

That is a great benefit because it not only makes it easier for you to update, but it makes it easier for a non-technical user to make small alterations to. Additionally, if you work as a web developer in a more freelance capacity, it is common for there to be a full-time web developer who has to maintain that site. Clean and simple to read code makes that an easy transition. We like it when people leave us easy to understand code, right? Let's return the favor.

Print Alternate Views

When you create a page using a table-layout, you are rather unfortunately locked into a certain layout. Developers who have created table-based websites, as most of us have at some point - particularly if you were in the the industry before the big tableless movement, know that you often have to create a separate printable version of your pages. This can be, needless to say, quite tiresome.

Ease of printing style control is a huge benefit with a tableless layout. You can easily create a single new printing style that applies to all your pages, instead of making them individually. That alone is a huge time saver, but there is more.

While you can control all elements with this approach, the biggest key is organization of information within the page itself. Using the example, let's assume that the display order we want all our pages to print using the following order: The page header first, the content next, the special news after that, then the link list, and then the footer. However! We still want it to display as it would normally when viewing (meaning the header at the top, the links on the left, content in the middle, news on the right, and footer at the bottom). With a table-based layout, you would have to create a new page to do that special printing organization because the print style will read your columns left to right. With a table-less layout, you are not bound by this. You can order the content in your page however you like, and still control the way it looks... all by using the CSS only!

Additionally, because we can put the content in whatever order we want in the HTML, and then move the content blocks around for website viewing using CSS - we can have ultimate control over presentation.

That is very important because the clean code, and ability to alter presentation, means that your site can be viewable by someone on a small mobile phone screen, a PDA, in all text format can be perfect for someone using a text-to-speech reader, or a Braille device, and since the code is clean, it is both backward compatible (with older browsers seeing mostly just the text) and forward compatible with new technologies to come. The flexibility and organization leads to being able to create a powerful website that takes advantage of some of the possibilities with XHTML, and adding in support in your pages for micro formats, or taking advantage of using RSS / ATOM feeds from your site to develop a base of regular readers.

Search Engine Optimization

Due to the fact that you can organize your most important content at the top of your page, without affecting the layout, your page can be better optimized for search engines. For instance, say that I have a navigation bar on the left side of the page that lists tons of parts of the site that are actually great keywords. I could move that navigation bar code higher up in my actual HTML, without changing the layout, because I'm using the CSS to position the navigation where I want it.

Those search engines can also more clearly find common words throughout your document without having to filter through code. Search engines prioritize websites that have a higher content to code ratio, so putting all your style elements into your external CSS style sheet makes your site highly content based to a search engine. Tableless layouts, as previously mentioned, decrease page size and loading time - another bonus to search engines.

Additionally, being able to take advantage of the RSS/ATOM feeds (see the section directly above) will aid you in some new technology for site indexing as used by all search engines called ROR. (ROR is an XML format summary of your website, like a sitemap, that search engines can access for additional information about your website.)

Presentation Flexibility

Making changes to a CSS based Tableless layout is simple. You can alter the CSS file only, changing as many styles and graphics as you want. The affects cascade through all the pages on your website, and eliminate the need for manually updating many pages.

Selling Yourself On Standards

Sometimes knowing how to code for standards, and create flexible tableless layouts is not enough. There are some web designers who meet with difficulties from their management. Most often those difficulties are rooted in the management being unaware of the benefits of using tableless content and CSS driven layout.

If you want to design for standards, but you work for a company that is not very forward-thinking in allowing you the time to work on the changes -- try this: Make them think about their pocket-book. Point out the cost saving benefits.

For instance, try grabbing a single page of existing code. Clean it up to standards. Compare the page size to before (including image optimization), and count the difference in bytes saved. Multiply that across the number of site pages, and the number of days per month. Then explain to them the amount of bandwidth cost saved monthly if this was done across the whole site. If that isn't enough, show them how quickly you can make changes to a website once it is CSS driven, and push the idea that you will be able to change the site more rapidly when there are needed updates, and you will have more time to focus on adding in new functionality to the site - instead of spending your time doing maintenance.