I have been socking my head against a wall for 6 hours now.
One of my remaining shared hosting website on a large host would show all sorts of craziness: broken CSS, endless errors, validation nightmares...
Plus the website scored C on Page Speed with massive red warnings.
It's odd, because usually I tend to tame W3 Total Cache quite well.
I have disabled everything in it except page / browser cache and minify and found out this HUGE generated code issue.
Whereas using v. 0.9.2.11 (including re-installing it after removing 0.9.3) W3 TC generates this code:
Couple of header lines <link rel="stylesheet" type="text/css" href="http://www.domain.tld/directory/wp-content/cache/minify/000000/d2874/default.include.f06f00.css" media="all" /><meta http-equiv="Content-Type" content="text/html; charset=UTF-8" /> ...
in version 0.9.3 it generates this wrong code:
Couple of header lines <link rel="stylesheet" type="text/css" href="http://www.domain.tld/directory/wp-content/cache/minify/000000/d2874/default.include.a0952a.css" media="all" /><meta http-equiv="Content-Type" content="text/html; charset=UTF-8" /> ... <link rel='stylesheet' id='admin-bar-css' href='http://www.domain.tld/directory/wp-includes/css/admin-bar.min.css?ver=3.6' type='text/css' media='all' /> <link rel='stylesheet' id='contact-form-7-css' href='http://www.domain.tld/directory/wp-content/plugins/contact-form-7/includes/css/styles.css?ver=3.5.2' type='text/css' media='all' /> <link rel='stylesheet' id='edd-styles-css' href='http://www.domain.tld/directory/wp-content/plugins/easy-digital-downloads/templates/edd.min.css?ver=1.7.2' type='text/css' media='all' />
Yes, you saw it right. 0.9.3 creates the minified file and then it imports every minified file a second time, like it is a non cached website that loads all the CSS and JS one by one. Plus, disregarding settings, it also adds a ?ver=N.N.N suffix to each, to annoy search engines as much as possible.
This duplication of course causes all sorts of disasters, double the bandwidth consumption and more http connections than a non cached website.
Therefore I warmly suggest anyone seeing oddities in their website since installing 0.9.3 to see if it's duplicating CSS and JS files like it did to me.