The standards conformance composite is determined by dividing the results of each test by the maximum score of that test, then multiplying by 100 to get a percentage. The percentage results of the three tests are then averaged together to achieve a composite grade.
Chrome takes first place on both operating systems with a B-. It is followed by Safari in second place on OS X with Opera and Firefox caught up in a tie for last, both achieving an equal C. Opera manages an extra percentage point on Windows 7 to place second with Firefox close behind in third. Last place in Windows 7 goes to Microsoft's own IE9 with the only failing grade.
The charts below are for the three standards conformance tests: Ecmascript Language test262, HTML5Test.com, and The CSS3 Test.
IE9 is significantly behind the curve in all three disciplines, while Chrome's better-than-average HTML5 and CSS3 scores allow Google to dominate standards conformance.