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:
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.
A CSS-based website will appear higher in the search engine rankings for three reasons:
A higher search engine ranking means more site visitors, which, provided your website is usable, should lead to an increase in enquiries or sales.
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 Nielsen).
CSS downloads faster than tables because:
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.
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.
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.