We have some HTML pages (local, not on a web server) that use the BASE element to identify a specific base directory that contains a bunch of common stylesheets and images.
Unfortunately, it looks like IE8's standards mode does not handle file:// URI's in the BASE element.
If you can run script inside your local pages, I'd suggest you use some simple javascript to loop through all your external elements (SCRIPT, IMG, LINK, IFRAME, FRAME) and fix up any scheme-less URIs (the ones that don't contain "://") using your desired BASE.