css adaptive background

When developing, modifying the d2admin login page. Use a background image, but the map is too big to ui (I may be a small computer screen Ha) can not be fully displayed on the page, so changes to your code, you can display a complete background.

Code is as follows:
background: URL (./ Image / img.jpg) NO-REPEAT 0px 0px;

background-size: cover;

 background-attachment: fixed;