image don't show at runtime ,while it works well in vs designer

I'm working on a web application in vs 2012 and I need to store the path of images found in a folder at desktop  in the sql database in order to retrieve them later in a gridview .I almost tried every way but at each time the image shows perfectly at designer but don't show at run-time.

I even tried to set the background image from outside folder and it also work at designer level but don't at runtime:       

:url("C:\Users\admin\Desktop\Gym\Images\3gurlz.png"); I am sure that the path is correct ,but don't know why it only work at designer level or it must be saved in the project file.

if anyone has any suggestions let me know plz