mod_pagespeed won't combine CSS and JS

For CSS Combine

As you are using Wordpress, you need to add a Function in function.php of Wordpress.

function remove_style_id($link) {        return preg_replace("/id='.*-css'/", "", $link);}add_filter('style_loader_tag', 'remove_style_id');

Wordpress writes ID="" Tags into the css link which pagespeed doesn´t like. So it will be ignored.

BUT It "could" cause Problems with a Plugin if a Javascript calls the ID, but regular no one will do it that way. So you´ll be safe.

You can permit IDs for css combining as of version 1.12.34.1, have a look at the documentation.

As wordpress adds -css to any ID, you can just add:

Apache:

ModPagespeedPermitIdsForCssCombining *-css

Nginx:

pagespeed PermitIdsForCssCombining *-css;

There appear to be a few issues preventing mod_pagespeed from combining resources on your site. First of all, many of your CSS files have id attributes, which will prevent the combine_css filter from functioning. HTML generally expects elements to have a single id attribute, and it's not clear what that should be if those CSS files are combined.

That doesn't explain why mod_pagespeed does not seem to be rewriting any CSS or JS resources on your page though. mod_pagespeed is able to rewrite the HTML, for example www.oktoberfest.it/?ModPagespeedFilters=collapse_whitespace is able to remove whitespace from the page. The issue is likely that mod_pagespeed is not able to fetch these resources internally. This can happen for a number of reasons, but look in your apache error_log for messages related to SERF.

The best fix for fetch related failures is to use the ModPagespeedLoadFromFile directive if your environment will allow it. Also have a look at this FAQ entry, which explains the problem. You can also try updating to beta release 1.4.26.1 or later, which includes a workaround for common loopback fetch errors.