The million+ most FAQ, should be answered by reading FAQ.
*Don't sweat it though, I probably would have asked sometime myself but I was lucky enough to see people get flamed for asking, and therefore got my answer, ahaead of time .
Coolant overflow warning. This thread can be locked now .
hahaha! its NEXT to the TEMP gauge, it even LOOKS like a radiator! lololol (Toyota must have anticipated cooling system problems because virtually no other cars have the coolant overflow warning light)