Fix some HTML markups.

"style" tag requires attribute "type" but it was not specified. Also,
some "br" tags was not closed.
balloon tag is allowed in wiki format.

html format doesn't allow it.
Beautify tables.

Tables used to have thick borders. Apply a style to make them tiny.
Make the 'active shared memory' table be like other tables.

It seems that someone forgot to add break lines after each item in the
table.
Make html format spec compliance.

Add head, body and meta tags to make it pass a html validator. XHTML 1.0
Strict was chosen because it is old enough for some ancient browsers.