Alright, This usually occurs when someone borrows your car, and tries to be nice and fill up the tank...but, not realizing it untill after its done, and not seeing the sentence "DIESEL FUEL ONLY" on the Fuel guage and on the Fuel cap, they put a nice amount of Gasoline into the tank.
Ok, heres the deal, Gasoline has a High Octane rating which keeps it from igniting at high temperatures..so all that will happen is the engine will run BAD and be hard to start, but if there is A LOT in there then it probrably wont start at all, and if it does...it will make a loud Unusual Diesel Clatter...So, SHUT IT OFF! the injection pump needs lubrication from the Diesel Fuel to prevent damage
Unfortunatly, There is no GASOLINE IN FUEL Light, but it will run bad and make unusual clatter noises...a good way to tell is smell the Fuel tank inlet for gasoline...or if someone told you there was cause they put it in..get it out as soon as possible!
If you Have GASOLINE IN your FUEL, Get it OUT!