Switch from xhtml to plain html.

Since that's the new way, according to Sam at least.
Add magic IE chants to all page tops.
More head-level additions.

Note that I used "image/x-icon" for the "shortcut icon" type, even
though it's different from the one used on the "icon" type right above
it.

Also, need to scan all the "@;" comments here: some might need to be in
the actual HTML output, and some look like leftovers from wherever this
HTML was ripped from that are not applicable.
Update the TODO html.