IE9 is an acronym for Internet Explorer version 9.
 

Upgrade to Internet Explorer 9

See this msdn blog page: http://blogs.msdn.com/b/ie/archive/2009/11/18/an-early-look-at-ie9-for-developers.aspx

You can download IE9 Product Guides at: http://www.microsoft.com/download/en/details.aspx?displaylang=en&id=12968

 See here about details for downloading and installing Internet Explorer 9.

Compare IE8 and IE9 here: Internet Explorer version 9.
 

Upgrade to Internet Explorer 9

See this msdn blog page: http://blogs.msdn.com/b/ie/archive/2009/11/18/an-early-look-at-ie9-for-developers.aspx

You can download IE9 Product Guides at: http://windows.microsoft.com/en-US/internet-explorer/products/ie-9/compare-browsers

See Also

Internet Explorer 9

Download and Install Internet Explorer 9


How to Set a Pop-up Window to Open in a New Tab in IE9