- to refer to a set of technologies that together form the future Open Web Platform. These technologies include HTML5 specification, CSS3, SVG, MathML, Geolocation, XmlHttpRequest, Context 2D, Web Fonts (WOFF) and others. The boundary of this set of technologies is informal and changes over time.
- to refer to the HTML5 specification, which is, of course, also part of the Open Web Platform.
Although it would be great if people used one term to refer to the specification and another term to refer to the set of specifications, in practice people use the term both ways.
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