How to show an image properly?

How to show an image properly?

Dear friends,
 
I am uploading a image and showing it to a fixed size(width='728' height='286')image box but images are not showing correctly as the actual image , even the large images seen faded or distort ,
is there any function or any property or something like this by which i can show a proper image in the image box.
 
If yes then pls share any link or your suggestion to do this,
 
thanks