W3C
The World Wide Web Consortium (W3C) develops interoperable technologies (specifications, guidelines, software, and tools) to lead the Web to its full potential.
http://www.w3.org/

Extensible Markup Language (XML)

Hypertext Markup Language (XHTML)
The mission of the XHTML2 Working Group is to fulfill the promise of XML for applying XHTML to a wide variety of platforms with proper attention paid to internationalization, accessibility, device-independence, usability and document structuring.

W3C Semantic Web Activity,
The Semantic Web provides a common framework that allows data to be shared and reused across application, enterprise, and community boundaries.

Amaya, the W3C's Web editor.
Download Amaya for Windows or Linux

SVG
SVG (Scalable Vector Graphics) is an open W3C standard for describing two-dimensional graphics.
SVG is a language for describing two-dimensional graphics and graphical applications in XML.
Drawing software, like Inkscape, saves drawings in SVG format.