If your toilet is leaking, and you’re not sure where it’s coming from, it’s time to do some detective work. Dry up the water regularly, and examine the area around the toilet.
If the bowl and tank are generally wet, there’s a good chance it’s condensation, caused by cold water constantly running into the toilet. If that’s the case, check to see whether the float ball is sitting low enough so that it shuts off the water before it reaches the top of the overflow tube in the middle of the tank. Lift the arm and see if it shuts off the water. If it does, adjust the screw or bend the bar to lower the ball. If you lift the arm, and the water doesn’t stop, it’s likely a diaphragm in the ballcock assembly (that structure to one side of the tank). You can replace the diaphragm by unscrewing the cap off the ballcock or you can replace the whole ballcock.
If the water comes on intermittently, it might also be a leaking or misaligned flapper. Realign or replace it, and clean the area it sits in with steel wool.
If the water’s leaking from the water supply line, tighten the nut where it joins the tank at the ballcock, or replace the line.
If it appears to be coming from the area where the tank joins the bowl, it might be a worn washer on the tank bolts. Tighten these — very gently — by screwing from inside the tank, holding the nuts below the tank. Never overtighten when working on a toilet; you can crack the porcelain.
More ideas next time.