W3C Semantic Web group's webapp implementation of pyRDFa: parse RDFa from a URL, uploaded file, or text area; get bookmarklets to parse RDFa directly from the current page.
The official CSS page at the W3 Consortium.
The "Learn & Use" page is crammed full of links to tutorials, articles, and events. The majority of resources are in English, but there appear to be a decent number in other languages as well.
Interaktive Informationsgrafik zur Entwicklung von Browsern und Webtechnologien. Die Darstellung umfasst die Entwicklung wichtiger Webbrowser seit 1993, darunter Mosaic, Netscape, Opera, Internet Explorer, Safari, Firefox und Chrome, sowie wichtige Entwicklungen im Bereich der Webtechnologie, beispielsweise HTML, CSS und JavaScript.
AChecker is a Web accessibility evalution tool designed to help Web content developers and Web application developers ensure their Web content is accessible to everyone regardless to the technology they may be using, or their abilities or disabilities.
The Functional Accessibilit Evaluator analyzes web resources for markup that is consistent with the use of DRES/CITES HTML best practices for development of functionally accessible web resources and resources that support interoperability. The HTML best practices are not a new standard, but rather a statement of techniques for implementation of the W3C Web Content Accessibility Guidelines and United States Federal Government Section 508 standards that not only improve accessibility for people with disabilities, but also the interoperability of web resources for everyone so all people benefit by having more options to access and use web resources.