Mustang GT 2005 won't start =( on 2005 Ford Mustang GT

I drove my GT yesterday as usual...to work, then to the Mall, I was on a car jam, then the supermarket. After that, when I tried to start it..NOTHING...just a "click"sound and everything else turns on (radio, lights, alarm), but the car just won't start! It has happened to me before, but this time nothing seems to start the car.HELP!!!

2 answers
Start with the battery. If a jump doesn't help, then you will work your way back up the starting/charging system to the starter, etc.

If it is not the battery, you should take it in to be worked on.
Sounds like a bad battery or a dirty/loose battery cable connection. You may also have a problem with the security system, but I would look into the battery first.
Have you tried jump starting it?