include() and current working directory

Hi, I'm using include to display a html file from a different directory to the current working directory. This page displays, but is missing all the CSS formating. I'm assuming this is because it can't find the CSS because it's in the different directory to the CWD. So, the easy way out is to move the CSS, but I've got heaps of these, and it makes it really messy. The PHP looks like this: include("xxx/index.htm"); the css is saved in the xxx folder. I'm open to any suggestions, ideas? Many thanks Matt