Google recently released Chrome 48 and yesterday Firefox 44 was released, with both of these new releases support for RC4 as an encryption protocol has been removed (due to several bugs being found in the cipher).

This means if your IBM Domino server is accessed over HTTPS (ie for iNotes or Domino applications) in order to support these new browsers it will need to be running Domino 9.0.1 Fix Pack 4 or Fix Pack 5, otherwise when users attempt to access the server, they will see the below.

Firefox