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The output of your command "$ file *.html" is:

Solaris.html: HTML document, ASCII text
contact.html: exported SGML document, ASCII text
head.html:    XHTML document text (version 1.0) XHTML document text (version 1.0), Unicode text, UTF-8 text, with very long lines (1024)
index.html:   XHTML document text (version 1.0) XHTML document text (version 1.0), ASCII text, with very long lines (318), with no line terminators
tail.html:    ASCII text