Web Experience Toolkit (WET) includes reusable components for building and maintaining innovative Web sites that are accessible, usable, and interoperable. These reusable components are open source software and free for use by departments and external Web communities
http://wet-boew.github.io/v4.0-ci/index-en.html
Accessibility
Conforms to WCAG 2.0 level AA Leverages WAI-ARIA to further enhance accessibility Assistive technology testing (Access Working Group)
Usability
Iterative approach to design Design patterns and usability testing (User Experience Working Group)
Interoperability
HTML5-first approach (leveraging native HTML5 support and filling support gaps with “polyfills”) Supporting a wide variety of browsers (IE, Firefox, Chrome, Safari, Opera) Building support for HTML data (RDFa 1.1 Lite, Schema.org)
Mobile friendly responsive design
Adapts to different screen sizes and device capabilities Touchscreen support Optimized for performance Building support for device-based mobile applications
Place WET 4 theme at or near the bottom of the plugin list.