Following the XHTML Path

webreference.com/xml/ - Xploring XML on WebReference.com

The main difference between HTML and XHTML is the structure of XHTML. XHTML is a more formalized structure of HTML 4.0 supporting all HTML 4.0 features with complete CSS and DOM support. The formalized style of XHTML coding allows ease of maintenance and future additions to any XHTML Web page or site. Loose and unstructured elements are not allowed in XHTML. For example, in XHTML you must use lower case tags for all HTML attributes and elements:

Another example of structured XHTML is unclosed elements. All XHTML elements must be closed out to produce a well-formed document. Well-formed (a term carried over from XML) simply means that all elements are nested and closed properly and follow strict guidelines in XML and XHTML. A good example is the paragraph element:

JavaScript and CSS are not allowed in XHTML documents. The XML parser will report a error if the XHTML page contains internal CSS or JavaScript coding. Any CSS or JavaScript can be accessed through a external file. Relocate the CSS and/or JavaScript to a separate file and cross link the XHTML page to it. Web page developers will find this actually helps to modularize the components of a Web site. Anytime you need to access CSS or JavaScript, simply link to the appropriate file from your XHTML code. Most developers find this style of Web site design to be easier to maintain and modify. Modularization of XHTML is one of the future features currently under review by W3C. For further information and specifications about XHTML 1.0, please refer to the following XHTML web sites:

webreference.com/xml/column6/ - XHTML vs HTML
www.w3.org/TR/xhtml1/ - XHTML 1.0 specifications
www.w3.org/TR/xhtml11/ - XHTML specifications under review

Now is the time to double check your HTML editor. Most current HTML editors have support for XHTML. Be sure to get the latest updates and version of your HTML editor. If your editor does support XHTML, then be certain to review all documentation and suggestions on the XHTML functions. Practice converting your Web pages from HTML to XHTML. Be sure to check your XHTML by submitting your Web page to the W3C XHTML Validator. (validator.w3.org) The validator will verify that your Web page follows all XHTML guidelines and will parse correctly.

Next: More on XHTML

This article originally appeared in the June 29, 2000 edition of the WebReference Update Newsletter.