I was testing and comparing the old and new versions of styles for validation, and the following line is missing in code-changes:
OVERALL_HEADER.HTML (find and remove)
<meta name="copyright" content="2000, 2002, 2005, 2007 phpBB Group" />

Some styles are being updated and submitted to StylesDB with the line, but in prosilver/subsilver2 3.0.9 the line has been removed.