XHTML - eXtensible Hypertext Markup Language
XHTML (eXtensible Hypertext Markup Language) and HTML (Hypertext Markup Language) are the programming languages that are used to create Web pages.
Basically, XHTML 1.1 is the current standard for Web page development and supercedes XHTML 1.0 and all versions of HTML. Many, if not most, Web developers are still coding in HTML even though XHTML has been around for quite some time. In the past, with HTML, it was possible to get away with a lot of sloppy coding and many still do. That has now changed under XHTML.
Why should I care if my Web site is in correct XHTML?
All browsers, such as Internet Explorer, know how to deal with correct XHTML/HTML. However, if it is incorrect, the browser has to repair the document, and since not all browsers repair documents in the same way, this introduces differences, so that your document may look and work differently on different browsers. Since there are hundreds of different browsers, and more coming all the time (not only on PCs, but also on PDAs, mobile phones, televisions, printers, even refrigerators), it is impossible to test your document on every browser. If incorrect Markup is used and your document doesn't work on a particular browser, then you are potentially losing business.
So Why Did We Switch to XHTML?
It's not so much an issue of "strict code" as it is an issue of compatibility and conformity. As Web Developers we must be moving with the flow in order to provide the highest level of service for our clients.
XHTML Guarantees Usability
Working with XHTML, we can ease the transition to the future, making life easier for ourselves and offering additional benefits to our clients including a guarantee that your Web site will be usable, regardless of the accessing platform.
Because the format is strict, the code is clean, and Web browsers are able to display the page more quickly than one with errors and unformatted code.
XHTML Improves Accessibility
XHTML provides greater control over documents viewed in a variety of browsers and other devices, i.e. cellular phones and Braille devices, which leads to better accessibility. Better accessibility leads to more page views and greater returns.
Whilst our clients might not initially be concerned with or may not have considered seeing their documents in anything other than a standard Web browser, the technology of the future demands portability to other platforms.