This is probably the single biggest change in the history of Internet Explorer and Mozilla Firefox.

Though hard to believe, you can now make not only your Mozilla Firefox look and behave just like Internet Explorer (without any of the problems), but you can even do something you would have never thought possible: test Web pages for compatibility with IE inside Firefox itself!

Once it is seen by enough developers, the eventuality will be tools to create identical Web pages followed by a patch to make Firefox itself render pages identical to Explorer by default.

That is the killer app.

There has been an enormous misunderstanding among Explorer developers that Mozilla browsers simply can’t render correctly.