duratecs runs really steady at "O" or about 1/4 like a fuel gauge
my zetec use to run at "M" or just under now it runs just over "M", will hit "L" in stop and go traffic
fan kicks in when it gets just above "L" or 212 F if you have OBDII and can scan that
but basically if your car doesn't show signs of over heating and the fans work correctly you have nothing to worry about, please search here and the zetec forums as this has been covered way to many times and you will get the same answers ....
remember the temp guage is not calibrated to a persice number for the needle location so it can vary from vehicle to vehicle it is calibrated to show in general where the temp is and to warn you if it gets to high