how write specifically syntax of path of image on background-image property, while the image is into a different folder?

Question

background-image:url() ??

Answer 1

If the css declarations are inlined (embeded in html file) paths are relative to this file directory (folder)...

if the declarations are linked in an external css file, paths are relative to the css file directory ;)

Answer 2

try to use two dots to go in parent folder

url('../img/1.jpg')