This product allows you do the following options
You can run the complete test suite on your browser to check the compliance to ECMA-262 standards.You can also browse trough the failed test case.
You can compare java script conformance of the various leading browsers in the market.
Now web developers can be more cautious while designing websites to make them compatible with multiple browsers. Google is committed to review and release multiple version periodically with updated test cases.
According to the latest sputnik test result released by Google, Opera 10.5 leads the race with only 78 failures. Microsoft IE 8 performed the worst (463 failures) . Next to Opera, Apple’s Safari (159 failures), Google’s Chrome (218 failures) and Mozilla’s Firefox (259 failures) leads respectively
Though the test are about conformance, not performance, the top 3 leading browsers are among the last three in conformance which is something they have to improve