Teach Safari to ignore case if necessary when opening local html file
If you do have your drive formatted as case sensitive, use Disk Utility (Applications->Disk Utility) to create a non-case sensitive disk image. Copy all the files over to said disk image and you should be good to go.

It's a little bit of a pain to mount the disk image when you need to look at the files, but probably far easier than attempting to normalize the upper/lower caseness of every filename &amp; href in the html.