Because XHTML is just an XML application, you can extend it simply by creating new elements and attributes. I'll take a look at an example here, creating a new element, <underlinedredtext>, that will style its contents as underlined red text. Here's how that element might be defined in a DTD:
<!ELEMENT underlinedredtext (#PCDATA)>
You can also add attributes to an element like this—I will do that here, calling the attribute underlinedredtextattribute:
<!ELEMENT underlinedredtext (#PCDATA)> <!ATTLIST underlinedredtext underlinedredtextattribute CDATA #IMPLIED >
This is a new element that I'm adding to XHTML. To include the rest of the XHTML 1.0 Transitional DTD, I'll create a new parameter ...