Please remove the attribute type="text/css" from ScriptmergerCss.php
Please remove for an better validation this in ScriptmergerCss.php:
Old: '<style media="' . $media . '" type="text/css">' . LF . "\t" . '/* <![CDATA[ */' . LF . "\t" . $cssProperties['content'] . LF . "\t" . '/* ]]> */' . LF . "\t" . '</style>' . LF;
New and better:
$content = LF . "\t" .
'<style media="' . $media . '" >' .
"\t" . '/* <![CDATA[ */' . LF .
"\t" . $cssProperties['content'] . LF .
"\t" . '/* ]]> */' . LF .
"\t" . '</style>' . LF;
. type is not good, the line break after too. The W3C validator don´t like it.</p> <p data-sourcepos="23:1-24:54">Your extension is the best for the speed optimizations. Google Page Speed like it :-) Thank you very much for this wunderfull extension !!!!</p>