if your toilet rocks to a different tune and you don't particularily want to replace the whole floor to fix the problem(which can be costly) , all you have to do is set the toilet as well as you can, pull out a tube of white silicone and squeeze out the whole tube around the perimeter making sure that your generous with it enough so that it gets underneath the edge of the toilet so it makes a gasket between the toilet and the floor. Next you put some dishsoap on a 1" putty knife and drag it around the circumference of the toilet to smooth out the silicone. The next day go back with a utility knife and carefully cut any excess silicone on the floor around the toilet and your done! That toilet will never rock again! Not only that but it will barely be noticeable. cheers,Derek
p.s. if you have a colored toilet, use clear silicone!