Ford Focus: what does the warning light (exclamation mark) mean?

This is a transmission warning- any other clues ? Recent tyre change or spare wheel change ? Loss of pressure in a tyre ?

This is NOT a Tyre pressure sensor warning!
Don't know why people post this when they haven't got the foggiest idea.
It is a fault associated with the drivetrain which includes from the injectors on the engine to the transmission and possibly just a sensor malfunction.
There are multiple errors possible with this fault.
Requires a diagnostic OBD2 port analysis of the ECU to clear the fault codes and further analysis.

that warning light is the message given to you by the vehicle ECU,and by using a scanner surely you will get the fault code given.

Right above the check engine light ?
Powertrain warning lamp ,is what factory service info calls it .
Powertrain Malfunction Indicator Lamp The powertrain malfunction indicator lamp illuminates when a DTC is registered in the PCM which does not affect exhaust emissions. This lamp will also illuminate if the fail-safe cooling strategy is invoked by the PCM.
Have vehicle checked for DTC'S - diagnostic trouble codes .

Hello chris...that light is a warning light telling you the ECU has detected a malfunction in the computer controlled mangement system. It could be any number of reasons, some more serious than others. You should have your vehicled scanned for codes. Even if the light has gone off, it has probably stored a code in the memory. With this newer system Ford is using, these store codes can cause more codes to set. So don't neglect getting it checked out for too long.
Good luck & i hope this helps.

need to be more specific with the exclamation light... color, description of what the light looks like with the exclamation.

Red usually means your brakes,
Orange should be coolant related

That symbol is the Low TIre Pressure Warning. It tells you that your tire pressures are low.

oil pressure light get the oil pump checked

This light is for multi funtion automatic transmisson cooling system

IT SOUNDS LIKE THE LOW TIRE PRESSURE WARNING LIGHT. CHECK YOUR TIRE PRESSURE IF IT IS LOW ADD AIR THIS SHOULD ALLOW THE LIGHT T GO OFF. ALSO, CHECK YOUR OWNERS MANUAL FOR AN EXPLAINATION OF WARNING LIGHTS.