Shortened file extension

Shortened index.html
to index.htm
CLASS attribute fails cross validation

The CLASS attribute in the HTML tag fails to validate against: ISO/IEC
15445:2000, HTML 2.0, HTML 3.2, HTML 4.01 Strict.
CHARSET attribute fails cross validation

The CHARSET attribute in the META tag fails to validate against:
ISO/IEC 15445:2000, HTML 2.0, HTML 3.2, HTML 4.01 Strict.
Attribute content does not require quotes.