I have this same problem. I use php includes for my header files, and the images need to specify / so that the display is relative to the root of the site I am currently editing.

I have multiple sites, with many images, so putting copies of image files in C isn't practical.

I use a folder to contain multiple independent websites, and unless the display can be set to recognize the root folder of each of those sites, the display option can't see the dependent files. All the addresses that are currently relative to root would have to be changed to absolute addresses.

How can you set preview to specify the root folder of the documents in a given web?
It is a basic issue and without it, the display option is crippled.