An implementation of Internet Explorer ECMAScript that supports distinct document modes (that separately implement other versions of the language, such as JScript 5.7 and JScript 5.8 functionality) can return a single value that does not vary among modes. The return value cannot be used as a reliable indicator of the availability or lack of availability of specific language features.
The ECMAScript implementations within Internet
Explorer 9 always return a value of
when Internet Explorer 9 is operating in Quirks, IE7, or IE8 document