darn those notices! :-)
the 2nd one is a type, can you on line 391 change
if (($this->already_minified!==true) && (apply_filters("autoptimize_css_do_minify", true))) {into
if (($this->alreadyminified!==true) && (apply_filters("autoptimize_css_do_minify", true))) {the first one is slightly more difficult, I'll look into that one of the following days.
thanks for reporting!
frank