What is XHTML+MathML?
First, XHTML is an XML language whose main purpose is to describe a Web page. It is a cleaned-up version of HTML and is officially supported by the WWW Consortium as the current standard. It is retro-compatible with the well-known HTML, so that existing Web browsers work equally well with XHTML and HTML.
Second, MathML is also an XML language aimed at describing mathematical formulas. It encodes the structure of mathematical expressions in a standard way, so that software can display or process them. Software developers are adopting MathML at a fast pace.
Thanks to its modular structure, XHTML is able to include MathML formulas interleaved with the text, and this union is called XHTML+MathML.
Which software can display XHTML+MathML?
The browsers of the Mozilla family can display XHTML+MathML, including Firefox and Netscape (version 7 or later recommended). These browsers run on several platforms including Linux and Windows.
Specific to the Windows platform, the free MathPlayer plug-in (version 2 recommended) from Design Science can be added to Microsoft Internet Explorer to allow displaying MathML formulas.
Other MathML implementations can be found in the MathML software list.