1. CSS Flexible Box Layout Module

    Method of positioning elements in horizontal or vertical stacks. Support includes all properties prefixed with `flex`, as well as `display: flex`, `display: inline-flex`, `align-content`, `align-items`, `align-self`, `justify-content` and `order`.

  2. WebAssembly Threads and Atomics

    An extension to WebAssembly adding shared memory and atomic memory operations

  3. XMLHttpRequest advanced features

    Updated functionality to the original XHR specification including things like file uploads, transfer progress information and the ability to send FormData. Previously known as [XMLHttpRequest Level 2](https://www.w3.org/TR/2012/WD-XMLHttpRequest-20120117/), these features now appear simply in the XMLHttpRequest spec.

  4. cssimportrule api: href

  5. htmlanchorelement api: href

  6. htmlanchorelement api: hreflang

  7. htmlareaelement api: href

  8. htmlbaseelement api: href

  9. htmllinkelement api: href

  10. htmllinkelement api: hreflang

  11. location api: href

  12. stylesheet api: href

  13. svgaelement api: href

  14. svgaelement api: hreflang

  15. svgfeimageelement api: href

  16. svgfilterelement api: href

  17. svggradientelement api: href

  18. svgimageelement api: href

  19. svgmpathelement api: href

  20. svgpatternelement api: href

  21. svgscriptelement api: href

  22. svgtextpathelement api: href

  23. svguseelement api: href

  24. url api: href

  25. workerlocation api: href

  26. html element: area: href

  27. html element: a: href

  28. html element: a: hreflang

  29. html element: a: href: `href = '#top'`

  30. html element: base: href

  31. html element: base: href: `data:` and `javascript:` urls are not allowed

  32. html element: base: href: relative uris.

  33. html element: hr

  34. html element: hr: align

  35. html element: hr: color

  36. html element: hr: `<hr>` in `<select>`

  37. html element: hr: noshade

  38. html element: hr: size

  39. html element: hr: width

  40. html element: link: href

  41. html element: link: hreflang

  42. svg element: a: href

  43. svg element: a: hreflang

  44. svg element: cursor: href

  45. svg element: feimage: href

  46. svg element: pattern: href

  47. svg element: radialgradient: href

  48. svg element: textpath: href

  49. svg element: use: href

  50. global_attributes: href