Burn at bottom of microwave

First try cleaning the burned mark off. Dip a scrubber in lemon juice and sprinkle salt on it; this is also great for burned coffee pots. The smell can be gotten rid of this way: Boil lemon peel in water, then put the water in a spray bottle. Not only will it make your microwave smell fresh but the lemon oil will make it easier to clean. If it still smells of burning rubber, take the back off and inspect the wiring. IF you see burned wiring, please do yourself a favor and replace the microwave!

Microwaves work by making the molecules in food get "excited"-they move more-meaning, if there IS rubber burning, then there will be minute molecules of rubber in your food, which is BAD for your immune system. If it's just burned chocolate, though, it is harmless unless you are allergic.