Any new Web pages should conform to XHTML. Also, Anyone with existing HTML files should begin converting them to the new standard.
|HTML 4 Syntax||XHTML Syntax|
|<img src="image.gif">||<img src="image.gif" />|
A summary of the differences between HTML 4 and XHTML is available from W3C, along with guidelines on how to insure your converted files will still be compatible with existing browsers.
A useful tool for automating conversion of your pages to the XHTML standard is W3C's Tidy program.
An excellent HTML editor with Tidy built in is HTML-Kit, available as freeware (yes, free) from Chami.com.
The need to convert existing files to the XHTML standard is not immediate - they will continue to work in existing browsers. In the long run, though, new browsers and new software for creating and working with Web pages will increasingly require the new syntax.