Got one of those toilets that rock around a bit? Time for a little DIY before it grows into a large problem. When a toilet rocks it deforms the wax ring that mates the bowl to the toilet flange in the floor which can create gaps that blackwater could potentially work out of. This obviously is not a desirable outcome. You dont want sewage under your flooring and wood does not get along well with water. If you have vinyl floors with a paper or felt backing the first indication of a problem will be discoloration in the flooring. This is mold growing on the back of the flooring and over time will work its way further and further from the toilet. If you have tile you may see some discoloration in the grout lines or you may see nothing at all. The leak can fester longer under tile without being noticed which can lead to considerable damage to the subfloor below. For hardwood floors, the first indication will be some checking and staining of the wood grain about 2/3rds the way back on the bowl base. I have seen toilets in foreclosed homes that rotted the floor so bad it would literally break through the subfloor on one side if one sat upon it and tip right over.
You want your flange bolts tight but not overtightened which can crack the porcelain. It is also a good idea to caulk around the base of the toilet but leave a gap around 6 inches long at the back so if water does build up in here it has somewhere to exit where you can spot it. If you have an unfinished area below the toilet it should look dry around the flange. Taking care of the little issues in the home can prevent large ones down the road...