I\'m using Yii framework and have a CSS file that uses some images for background and similar.
Other PHP code can use Yii::app()->request->baseUrl to prefix the resource
The paths to images in CSS files are always relative to the CSS file, not to the page referencing the CSS file.
So it shouldn't matter that you are using the CSS file in HTML pages at different path depths, as it always looks from the location of the CSS.
For example, if your CSS file is in /Content/Css
and your images are in /Content/Images
then you should always reference your images as url(../Images/something.png)
.