According to Adrian Bateman, Program Manager, IE9 passes approximately 98% of all CSS 2.1 tests, with the RC of the CSS 2.1 Test Suite launched on Sep'17. "On [Oct'6th], Microsoft submitted CSS 2.1 implementation report for IE9 Beta showing that IE9 passes 18960 of 19403 tests (97.7%)," Bateman explained.
"It feels like a long time since we submitted our first batch of CSS 2.1 tests alongside IE8 Beta."
Microsoft and rest of browser makers have been working to submit their implementation reports in response to release of the CSS 2.1 Test Suite RC.
The deadline set by World Wide Web Consortium (W3C) for browser vendors to respond is Oct'18th, with the working group's template since Sep'17th.
"the real excitement comes from the knowledge that the CSS working group can focus attention solely on the new CSS3 modules that bring richer graphics to the web."