The "mouth of the house" and is usually the FACING direction and the back of the home or known as the sitting direction is equally important.
For a landed property, the main door should at least open inwards. If the home has a back door this back door should open inwards also. This excludes the grille protecting the backdoor. If the house does not have a back door; then this is considered as a neutral position.If there is a straight direct path from the main door towards the back of the house, then it is best to have a back door instead of just an opening at the back yard area.
Cheers. Peter
* Amended on 21/2/2011 at 09:21am