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After starting the testsuite it will automatically run a large number of small tests which will determine if your browser is compatible with a large number of CSS selectors. If it is not compatible with a particular selector it is marked as such. You can click on each selector to see the results, including a small example and explaination for each of tests. Because it is technically not possible to simulate certain user interactions the test is limited to selectors that are not dependant on user interactions. So this testsuite does not include tests for the following selectors: :hover, :active, :focus and :selection.