first of all thanks to ceryni, stwert and off course ctbram for your help but sorry to say that i have still not figured it out.
Ceryni. which is this menu where we can change the visibility as you mentioned in your reply.
well, i was going through this tutorial on car modelling and saw that the tutor was switching to back and front easily in Panels--- orthographic... (Please see the attached image.The image is from the exercise files.).
I checked and dont find any back command as in the photograph.
Ctbram... (the name of the view port mentions back for the back image)