To make sure you always have the proper path to images (etc.), start at the root and work your way down. For example, say I have a background image in a directory called images, a subdirectory of my weblog's root. I might point to it this way in my css:
This works as long as a page resides in the directory where "images" is a subdirectory. Using mod_rewrite places pages (virtually) in other subdirectories, so the path to the images directory becomes invalid. To deal with this, I provide an absolute path to my background image, like so:
The slash (/) before images starts the directory path at the root, and now will always be located by a page.