Denis Ryabov

Could you check your error_log file for related error messages? Usually 500 error is related to some error in PHP (WP or plugins), and it should be logged.

Could you try to disable “Load external files” option in the “Leverage browser caching” section of Advanced tab on PageSpeed Ninja settings page?

Do you use Apache or Nginx webserver? Do settings of your webserver allow to run PHP scripts in s directory (in the document root of the website)? Is there related message in webserver’s error_log file?

It’s necessary to clear s directory together with wp-content/plugins/psn-pagespeed-ninja/ress/cache (and wp-content/plugins/psn-pagespeed-ninja/cache if server-side page caching is enabled).

Usually, many files are generated in the case of dynamically inserted <script> or <style> tags that vary from page to page, and it is recommended to disable “Merge embedded styles” and “Merge embedded scripts” options to exclude them from merging.

@kuba739 One of optimizations, generation of above-the-fold CSS, is used on homepage only (note that other optimizations are used on all pages). That’s why homepage usually has higher score in Google’s PageSpeed Insight tool. Could you send us link to your website to check why exactly PageSpeed Ninja doesn’t improve inner pages?

And as to “Argument 1 passed to DOMNode::appendChild() must be an instance of DOMNode” error in your first post, do you use the latest version of PageSpeed Ninja? It looks like this error corresponds to older releases, because of abovethefold.css was refactored significantly in the recent releases.

PageSpeed Ninja has a possibility to generate Above-the-fold case both locally (in your browser, suitable for local website) and in the cloud (for possibility to regenerate it daily). See “Eliminate render-blocking JavaScript and CSS in above-the-fold content” section in the Advanced tab of plugin’s settings page.

In the general case: No. PageSpeed implements the same optimizations (and more). But not it is in the beta stage now, so if you think that other plugins do it better, why not to continue to use them?

1. Scores are loaded from api.google.com, and maybe it is actually blocked in China. Anyway, Google’s PageSpeed Insight service is not opensource, so we cannot duplicate it on our server. In this case you can use other testing tools, but it is not so convenient.

2. Is option “Local above-the-fold generation” (Advanced/Eliminate render-blocking JavaScript and CSS in above-the-fold content) enabled? If yes, website is loaded in a hidden iframe with disabled javascripts, and processed in your browser (WebKit/Blink-based one is recommended). Otherwise, a request is sent to our server that does the same in a cloud (but this way doesn’t work for local or intranet websites).

3. Pagespeed module in Apache and Nginx doesn’t generate Above-the-fold CSS (include style necessary for initially visible part of the page only), it generates Critical CSS only (include all CSS used on the page). In general, Critical CSS may be much larger, then Above-the-fold CSS, but in few rare cases (e.g. if page uses horizontal scrolling) there may be a flash/relayout of content after full styles are loaded.

4. “WordPress multisite is not supported” means that the latest released version was not tested in Multisite mode. At least, there may be some issues with caching, because of the plugin stores some cached data in its directory..

1. Switch from XML parser in Advanced settings to Stream one. This error will be fixed in the next release.

2a. Google API issue is most likely related to other optimization tool (maybe pagespeed module, hard to detect it exactly).

2b. Errors with keyword “sandboxed” are expected and related to in-browser above-the-fold CSS generation (JavaScript is disabled to speed up this procedure).

3. Pagespeed module and this plugin have many similar optimizations, I’m not sure about significant benefits from using both of them.

4. Nginx is supported, but unlike Apache, where it is possible to enable many optimizations in .htaccess file, Nginx requires to modify config file “manually”. We are going to prepare a config code snippet for Nginx further.

5. Not all JS can be loaded asynchronously. We have experimental option “Non-blocking Javascript” in the “Eliminate render-blocking JavaScript and CSS in above-the-fold content” section, you can try it, but we wouldn’t recommend to use it right now.

6. We use our own Above-the-fold CSS generation server, but in addition to it, we would like to implement a solution to do it directly it the browser. Hope it will be much stable in further releases.

7. WordPress multisite is not supported now, but we are working in this direction.

502 and 522 error codes most likely mean that there is a frontend server that has very short timeout for waiting backend server finished its work. PageSpeed Ninja may require quite a long time to optimize website first time (but results are cached, so further requests should be processed faster).

PageSpeed Ninja restores all settings being deactivated, and restores all optimized image files to original versions being uninstalled.

Maybe you have a kind of caching reverse proxy server, that cached old response from actual server. Could you explain some details of how your backend is set up?

What the cache did you clear? (browser’s, some other, …)

I latest releases of PageSpeed Ninja we made some fixes to Google Fonts loading, so that it should work better (i.e. more stable) and faster. You can choose between FOIT (flash of invisible text, default behavior in browsers) and FOUT (flash of unstyled text).

As to unstyled content, it may be related to above-the-fold CSS. In some cases above-the-fold CSS is generated incorrectly, or the page requires some javascript execution before rendering. In such cases “Above-the-fold CSS” feature should be disabled (see “Eliminate render-blocking JavaScript and CSS in above-the-fold content” section in the “Advanced” settings tab).

This issue has been fixed in PageSpeed Ninja 0.9.19. Could you check it?

@wer0ckz Multisite is not supported yet.