Yet more nesting problems fixed (Ticket 12036, "Incorrect work with limited set of tags"). Thanks to Igor Lobanov for reporting and Michele Beltrame for helping out.
Added (empty) attribute 'alt' to img-tags, to make it more W3C-valid Thanks to Michele Beltrame for reporting and patching.
Added case insensative tag matching Thanks to Denny Daugherty for reporting and patching.
Minor code changes (killing unwanted whitespaces).