fwiw, there was an IRC discussion related to the favicons and their sizes, and
it turned out that for IE9/MS one should have this:

  Recommended16x16, 32x32, 48x48
Optimal16x16, 24x24, 32x32, 64x64



http://msdn.microsoft.com/en-us/library/ie/gg491740%28v=vs.85%29.aspx