Although CSS layouts have been around for years, they haven't become so commonplace until recently. This was basically due to limited browser support (especially from Netscape 4) - nowadays though, CSS 2.0 (which introduced positioning) is compatible with over 99% of browsers out there (check out the browser stats over at The Counter). 

So, why should you convert your website from its current table-based layout to a CSS layout? It'll make you money. Simple really. And here's four reasons to explain why:

Reduced bandwidth costs 

Web pages using CSS for layout tend to have much smaller file sizes than those using tabular layouts. It's not unusual to see reductions of 50% or more in file size when switching from tables to CSS. Smaller file sizes obviously mean reduced bandwidth costs, which for high traffic sites can mean enormous savings.

The main reason for this dramatic decrease in file size is that presentation information is placed in the external CSS document, called up once when the homepage loads up and then cached (stored) on to the user's computer. Table layouts on the other hand, place all presentation information inside each HTML, which is then called up and downloaded for every page on the site.

Additionally, CSS can be used to replace JavaScript image rollovers, again allowing a large reduction in overall page size. 

A higher search engine ranking 

A CSS-based website will appear higher in the search engine rankings for three reasons:

• The code is cleaner and therefore more accessible to search engines
• Important content can be placed at the top of the HTML document
• There is a greater density of content compared to coding

A higher search engine ranking means more site visitors, which, provided your website is usable, should lead to an increase in enquiries or sales.

Faster download speed

A faster download speed will make you money? Well, yes. Slow download speed is often cited as one of the biggest usability complaints for websites. A faster download speed therefore leads to increased usability, and a web usability redesign can increase the sales/conversion rate by 100% (source: Jakob Nielson).

CSS downloads faster than tables because:

• The code is cleaner and therefore more accessible to search engines
• Browsers read through tables twice before displaying their contents, once to work out their structure and once to determine their content
• Tables appear on the screen all in one go - no part of the table will appear until the entire table is downloaded and rendered
• Tables encourage the use of spacer images to aid with positioning
• CSS generally requires less code than cumbersome tables
• All code to do with the layout can be placed in an external CSS document, which will be called up just once and then cached (stored) on the user's computer; table layout, stored in each HTML document, must be loaded up each time a new page downloads
• With CSS you can control the order items download on to the screen - make the content appear before slow-loading images and your site users will definitely appreciate it

Increase in reach 

The more people you can reach, the more visitors you'll get to your site and the more enquiries or sales you should get. A CSS-based website is compatible with PDAs, mobile phones, in-car browsers and WebTV. Don't underestimate the importance of this: In 2008 alone an estimated 58 million PDAs will be sold (source: eTForecast) and one third of the world's population will own a wireless device (source: ClickZ).

You can make an additional CSS document specifically for handheld devices, which will be called up in place of the regular CSS document, thereby ensuring your website is accessible to this lucrative market. This isn't possible with a tabular layout.

Conclusion: Switch to CSS! 

Switching your website from a table layout to a CSS layout can be a long, arduous process, especially for large websites. Given the money making possibilities though, it could very well prove to be well worth it. 

Trenton Moss, Webcredible - usability & accessibility

Hi Trenton

We're just redesiging this site (and its information architecture) at the moment and part of the change is to move from tables-based design to using CSS. 

All of the reasons that you give are very valid. Of course, improved accessibility is another motivating factor and you could argue that this will make you money by giving you greater reach to users with disabilities. 

The other point you didn't make explicitly within the 'speed' benefits is the resulting increase in page impressions. Once we've implemented the CSS we'll be looking at metrics like average number of page views per visit, and % of visits which view a single page only, to see if the increased speed also improves site 'engagement' rates as well as increases the no. of page views whilst the number of visits remains constant. 

We fully expect this to be the case. When we moved server infrastructure a few months ago, resulting in a faster and more reliable site, we were able to directly correlate site speed with an improvement in the metrics above. 

Currently we don't sell advertising so an increase in page views per session isn't that exciting to us. But imagine you are a big online publisher. A 10% increase in the average no. of page views / visit could make a huge difference to the amount of inventory you have to sell. So CSS speed would directly contribute commercially. 

We'll let you know what we find out...!

Ashley Friedlein
CEO
E-consultancy.com