How to get rid of the brown stain from my oven door?

Inside? Just leave the oven door open, take some paper towels and lay them over the spot, pour white vinegar over the towels until they are saturated and "pools" a bit. Give it 15 minutes ro half hour and wipe up. Then rinse with clean water. Or - if you use Magic Eraser pads, that would work too.

Make a mixture of baking soda and white vinegar into a paste and apply to the stain leaving on over night. Then wipe clean.

Here are some really helpful answers : http://www.hometalk.com/diy/clean/appliances/q-how-do-you-clean-the-glass-on-the-oven-door-1091550

Is it on the inside or outside of the oven?

Use the same product you use to clean glass-top stove. I currently use Weiman Glass Heavy Duty Cook Top cleaner & polish.

I did a self clean on my oven and the plastic on the top of my oven door turned brown how do I get rid of this?