My 2005 ford focus has a red light that just came on. It looks like a lock and now it wont start. What is this?

This is the key security system. Somehow youv'e set it off. Used the wrong key tried to open the door with the alarm on. Opened the door or trunk from the inside after locking it from the outside. If your the real owner of the car it'll be no problem to get it fixed. If you have the correct key lock the doors from the outside with the key and lock it twice ( the doors ( all of them ) should lock). Leave the car alone for a minute, maybe 5. Then unlock the door twice, all the doors should unlock the second time. Enter the car and start it with the key. If you with a remote door lock fob that can work too. If this fails then try a different door or even the trunk. Sometimes the driver doorlock switch wears out or gets ice in it and unlocking a different door or useing the remote can get you going again.