Duplicate ID's can mess up the preview

Some ID's in preview.html are the same as in page.tpl.php - namely for main-menu and the footer-wrapper etc, this can (not always, can't pinpoint the exact conditions) really screw up the preview... its also invalid markup, not so good eh?

Easy fix, change the ID's in preview.html. This looks like a big patch but really its not, its more of a cleanup which should have really been done in the earlier preview patch, but was overlooked. So in effect this patch does two things:

1. Fix the duplicated invalid ID's
2. Cleanup preview.css (most selectors where way over specified).

I think this is pretty major, it can really mess up the preview and is not tolerable for our default theme.