[FROM OP:] The specific question the Court will decide is: "Whether the court of appeals erred in holding that Microsoft’s invalidity defense must be proved by clear and convincing evidence." (From http://www.scribd.com/doc/36934612/Microsoft-i4i-Cert-Petition-patent-2010.)
For more about how cert petitions work, see http://en.wikipedia.org/wiki/Certiorari.
Hat tip: Stanford law prof Mark Lemley http://www.law.stanford.edu/directory/profile/38/