Accessing Image On CSS with Codeigniter

My file structure is

Code:

application

assets

assets > catalog

assets > catalog > theme

assets > catalog > theme > default

assets > catalog > theme > default > stylesheets > default.css

assets > catalog > images > holder.png

system

index.php

I need to access the image on my css but I cannot seem to get path.

What would be the correct path using the background url

Code:

body {
    padding-top: 64px;
    /*background: #E7E7E7;*/
    background: url('../assets/catalog/images/holder.png');
}

There's only one rule - please don't tell anyone to go and read the manual.  Sometimes the manual just SUCKS!