Frank Goossens on "[Plugin: Autoptimize] CSS and JS files are ignored during minification"

lenua; if you open up /wp-content/plugins/autoptimize/classes/autoptimizeStyle.php and on line 446 replace

$newurl = AUTOPTIMIZE_WP_ROOT_URL.str_replace('//','/',$dir.'/'.$url);

with

$newurl = preg_replace('/https?:/','',AUTOPTIMIZE_WP_ROOT_URL.str_replace('//','/',$dir.'/'.$url));

then the local font-urls (and the background images, if any) should be served from a protocol-less URL, as suggested by Ross (webaware).