relative links to i.e. images

How come I can not use a relative url to for example a background image?

For example:

background:url(“../logo-boom-boek_600.jpg”);

instead of:

background:url(http://localhost/wordpress_natuurschool/logo-boom-boek_600.jpg);

It would make moving the site from local to online so much less work!
What am I doing wrong?
Thanks, Bastienne