XHTML 1.0 Provides a Foundation for Device-Independent Web Access

If extensibility is likely to lead to more complicated pages and larger programs, the portability advantage means that Web pages can now be made simpler than they were before so that small devices can handle them. This is important for mobile devices and possibly household devices that contain microprocessors with embedded programming and smaller memories.

XHTML defines several levels of possible markup complexity and each document states its level of complexity at the beginning. Programs in microdevices might expect XHTML-coded files that state the simplest level of complexity so that they could be handled by a small program and memory. In addition to its extensibility, moving from HTML to XML via XHTML 1.0 lays the foundation for making Web content available to millions more users. People browsing the Web with cell phones or other mobile devices want Web content tailored to their needs. People with disabilities need ways to transform content into accessible formats.

There are increasingly new kinds of browsers: Digital TVs, handhelds, phones and cars, that won't have the processing power of desktop PCs and they will be less able to cope with malformed markup. So there's pressure to subset HTML for simple clients, and there's also pressure to extend HTML for "richer clients" (W3C's terminology for more powerful computers and browsers, not customers with a lot of money).

XHTML 1.0 provides the basis for a family of document types that will extend and/or subset XHTML, in order to support a wide range of new devices and applications. Efforts are underway to define modules and specify a mechanism for combining them. End-users and authors alike will benefit from work on describing the capabilities and user preferences for particular devices, e.g. display characteristics and information on the kinds of graphics formats supported, the HTML modules used, and style sheets support, etc.

XML documents can already be transformed using Extensible Stylesheet Language Transformation (XSLT), and rendered using independent style sheets such as CSS style sheets. XHTML 1.1, already under development, coupled with device-specific style sheets and Composite Capability/Preference Profiles (CC/PP) - a protocol which allows a user to describe both user preferences and device capabilities - will bring mobile and other devices to the Web as full participants.

XHTML 1.0 Combines the Familiarity of HTML with the Power of XML
Introduction to XHTML, with eXamples
Introduction to XHTML: Extensible Markup Language