page looks fine in IE 11, crap all over the place in Firefox.

What have you got in the site where you need to specify "This website is best viewed with Internet Explorer"? IE is no longer the browser of choice and you shouldn't do anything at all to prevent visitors using their browser of choice.

have you tried deleting ALL the files from the server, then doing a local publish and using Filezilla to upload the site? I have never been over happy with NOF's ability to upload a site.