1. Creating an XHTML document

The File → New dialog box allows you to choose between the following document templates:

XHTML Version	Template Name	Description
1.0	XHTML Page (Strict)	File having a `.xhtml` suffix, starting with an XML declaration (`<?xml version="1.0"?>`) and a `<!DOCTYPE>` pointing to the XHTML 1.0 Strict DTD.
	HTML Page (Strict)	File having a `.html` suffix, having no XML declaration^[a] and starting with a `<!DOCTYPE>` pointing to the XHTML 1.0 Strict DTD. This document template is a well-formed, valid XHTML file which is intended to be seen by Web browsers as an HTML file.
	XHTML Page (Transitional)	File having a `.xhtml` suffix, starting with an XML declaration and a `<!DOCTYPE>` pointing to the XHTML 1.0 Transitional DTD.
	HTML Page (Transitional)	File having a `.html` suffix, having no XML declaration and starting with a `<!DOCTYPE>` pointing to the XHTML 1.0 Transitional DTD. This document template is a well-formed, valid XHTML file which is intended to be seen by Web browsers as an HTML file.
1.1	XHTML Page	File having a `.xhtml` suffix, starting with an XML declaration and a `<!DOCTYPE>` pointing to the XHTML 1.1 DTD.
1.1	HTML Page	File having a `.html` suffix, having no XML declaration and starting with a `<!DOCTYPE>` pointing to the XHTML 1.1 DTD. This document template is a well-formed, valid XHTML file which is intended to be seen by Web browsers as an HTML file.
5.x	XHTML Page	File having a `.xhtml` suffix, starting with an XML declaration followed by `<!DOCTYPE html>` and conforming to an XHTML 5 XML Schema and Schematron developed by XMLmind. More information in About the XHTML 5 XML Schema and Schematron developed by XMLmind.
5.x	HTML Page	File having a `.html` suffix, having no XML declaration, starting with `<!DOCTYPE html>` and conforming to an XHTML 5 XML Schema and Schematron developed by XMLmind. More information in About the XHTML 5 XML Schema and Schematron developed by XMLmind. This document template is a well-formed, valid XHTML file which is intended to be seen by Web browsers as an HTML file.
^[a]This implies that the encoding of the file must be UTF-8 for this file to be successfully opened in an XML editor. This is enforced by the fact that all document templates called "HTML Page" contain: <meta content="text/html; charset=UTF-8" http-equiv="Content-Type" />

All the above document templates should be highly interchangeable between Web browsers and XML editors, however it is worth keeping in mind the following points:

If you want to feed your XHTML document directly to a Web browser, choose a document template called "HTML Page".
If you want to feed your XHTML document directly to a Web browser but your document also contains MathML, choose a document template called "XHTML Page".
If your XHTML document is a building block which is intended to be processed by an XML based publishing system, choose a document template called "XHTML Page".
More information in Activating Browser Modes with Doctype.

About the XHTML 5 XML Schema and Schematron developed by XMLmind

	About the XHTML 5 XML Schema and Schematron developed by XMLmind
Combined together the XHTML 5 XML Schema and Schematron developed by XMLmind^[1] implement most of the conformance requirements for authors specified in the HTML Living Standard (starting from the 2019-07-18 update). There are differences though: Attribute `id` may not contain space characters. Attributes like `class`, `rel`, `itemref`, etc which contain a list of tokens may not be completely empty. For compatibility with older HTML 5.x W3C Recommendations: The `table` element may have a `border="1"` or `border=""` attribute (which both means: table has a border). The `style` element may have a `type="text/css"` or `type=""` attribute (which both means: it's a CSS stylesheet). Note that our in-house XHTML 5 XML Schema supports `data-` attributes, ARIA `role` and `aria-` attributes and also custom elements.

Combined together the XHTML 5 XML Schema and Schematron developed by XMLmind^[1] implement most of the conformance requirements for authors specified in the HTML Living Standard (starting from the 2019-07-18 update). There are differences though:

Attribute id may not contain space characters.
Attributes like class, rel, itemref, etc which contain a list of tokens may not be completely empty.
For compatibility with older HTML 5.x W3C Recommendations:
- The table element may have a border="1" or border="" attribute (which both means: table has a border).
- The style element may have a type="text/css" or type="" attribute (which both means: it's a CSS stylesheet).

Note that our in-house XHTML 5 XML Schema supports data-* attributes, ARIA role and aria-* attributes and also custom elements.

^[1]These are found in XXE_install_dir/addon/config/xhtml/xsd/5/xhtml5.xsd (XML schema) and xhtml5.sch (Schematron).


XMLmind XML Editor - XHTML Support		2. Opening an existing XHTML document