If you are still designing with tables then you are missing out on a lot of the benefits of cascading style sheets (CSS). Tables were not supposed to be used for designing but unfortunately it has been the standard for a long time.
Not any more.
1. Separate content from presentation. An external style sheet can contain all the styles for your web site, then if you want to change the content you only have to edit one style sheet. This is great for a web site that
contains hundreds or thousands of pages.
Imagine if you had to edit each page..it would take you forever.
2. Google benefits. Google gives more weight to content closer to the top of your HTML document. Search engines spider the content that comes first in your source code. With CSS you can easily structure the
content to appear first with the rest of the source code following it. This will help outrank your competitors who may have their navigation appear first and their content last..
3. Fast loading pages. Tables slow down the loading of your pages because the spider has to crawl through each table. If your tables are nested inside each other your page will load even more slowly. Designing
CSS-based web pages will speed up the loading of your pages considerably because the styles are all contained in one style sheet.
4. Small file size. CSS will reduce the file size of your html document. If you look at a web page that is designed with CSS you will notice that the size is very small compared to one designed with lots of tables. This
also helps reduce load times.
5. Reduce clutter. CSS allows you to get rid of a lot of extraneous html code therefore making your site code neater and cleaner. This makes it easy to alter the code if you need to make edits.
be seen. You can often achieve the same affect with CSS navigation. These allow for rollovers and other pretty affects and are much more user friendly.
7. Accessibility. If you use CSS2’s aural properties it provides information to non-sighted users and voice-browser users. The CSS2 “media types” (used with @media rules) allow authors and users to design style
sheets that will cause documents to render more appropriately for certain devices such as braille devices, speech synthesizers, or tty (text telephone) devices.
Learn more about Accessibility Features of CSS
8. Save time. CSS will allow you to design your site much faster than tables because there are some styles you can use for every site.
I store “often used” CSS snippets in a special file where I can easily access them for any site I design.
9. Save money. CSS will shorten the project development process and eliminate design obstacles that occur from using tables. If designing many web sites you will be able to use the same style sheets or just make a
few modifications to them. You will still charge for the design project but it won’t take as long as when using tables thus making you more money in a shorter time period.
10. Flexibility of design. You can use pixel precision in your web site designs. By adjusting the margins and padding of the CSS you can easily adjust the position of your content.
You can also create very modern designs that can’t be duplicated with tables. For example you can use a background image for a header then place your content over it using the H1 tag for better page optimization.
11. Way of the future. The future of the web is moving towards better accessibility with web sites so they can be viewed by as many people as possible.
This may be enforced in future web standards therefore if your web site is still using tables or deprecated tags it may become obsolete or disappear from the search engines.
This could really hurt your business.
12. Print friendly. When a user chooses to print a web page an alternative CSS document can be called up. This document can specify that formatting, images and navigation disappear and just the page content
appear on the printed version.
See creating print style sheets
If your site is still mostly using tables for its design, you may want to consider doing a redesign. It may take a lot of work now but if you leave it for too long
it will be MUCH MORE work plus will be missing out on all the benefits of CSS outlined in the points mentioned above.