mirror ing problem

hi im modeling a car and i want to mirror it but when ever i do the part of the car that has been mirrored end up going under or above or next to on some random angle which is totally what i dont want.

heres the blend file if you want it http://www.2shared.com/file/yfKmq8Wd/911.html

does the mirrored car object when it has this problem does it create extra vertices over or under the mesh you modeled. if so i have been having the same problem and yes it is very frustrating.

yes annoyingly

You need to (1) apply the rotation to the object (Ctrl+A‚ÜíRotation to ObData) and (2) place the object centre on the mirror plane (in the middle of the car.)

thanks mat that worked awesomely