2001 Ford Focus leakage

i have the problem that appears to me recently since one week ago.the problem is that when my car's engine becomes completely cold like if i drive it whole day and arrive home and i see a small circle underneath my car engine .its the coolant .i have no problem with the controls of the car .the car is performing good as new.but when my car's engine becomes hot, the coolant stops leaking and it happens until car's engine is hot .when the engine becomes cool it starts dripping again continuesly uaually second by second