Toilet Shut-Off Valve Not Working
Make sure the valve stem is turning and not just the handle. Spraying a little WD-40 in there sure can't hurt. If the valve still won't completely shut off, you'll have to find your whole house valve which is usually on an outside wall in the vicinity of your water meter. These gate valves are notorious for failing too  so don't be surprised if they don't work too. If that's the case, there is usually another valve on the line side of your water meter that you should be able to operate. If not, call your water company and they will operate it for you. So if you get your water shut off, this is a great time to replace any of these valves that failed to do their job. good luck.