The first bird: table-less mark-up
It's important to remember that the benefits of XHTML and CSS move beyond these features: by having table-less mark-up, users can quickly and easily find desired information. Usually, when viewing a website in a hand held device, the screen resolution is reduced. This means that trying to find the main content of a page can be tedious. But by positioning your main content as close to the top of the page as possible, honing in on much-needed information is vastly easier. This results in a better user experience, which could in turn account for return visits.
The second bird: accessibility
In terms of accessibility, using XHTML and CSS can work wonders. For example, visually impaired users can now browse and navigate though a website with greater ease using features such as tab browsing and access keys. Access keys, for instance, work when a letter or number is assigned to an "access key" link. This allows the user to quickly jump to that link, when the command is executed on the keyboard.
The third bird: search engine optimisation
The benefits of using XHTML and CSS in the realm of search engine optimisation are more than noticeable. When using XHTML and CSS, the amount of code needed to mark-up a website is reduced immensely, and this in turn improves the rate at which a search engine can spider your website.
Moreover, XHTML and CSS can improve download speeds. If your site has a heavy mark-up, you'll have a larger file size and thus slower speeds. But if you link an external CSS with all design factors inside it, your browser will cache the file. That means that when a user visits another page, the browser won't have to download the file again. It will instead retrieve the file from the cache, speeding up the loading process and improving user experience.
The reduction of the amount of code benefits hand held users too. Hand held devices generally have slower connection speeds, so if the file size of a page is reduced, it will load faster on a user's device.
In conclusion, by designing a website in XHTML and CSS, as well as using some of the great W3C accessibility guidelines, any website is sure to benefit.
