Error message appearing on page editor

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  • #46746
    Power User

    An error message just began appearing on my Page and Post edit screens:
    Failed to load content css: http://URL/wp-admin/admin-ajax.php/?action=dynamic_styles

    How can I troubleshoot this?


    I have exact the same problem. It’s seems to be a problem with the update to WordPress 4.8. What can I do? Downgrading to earlier version of WordPress doesn’t have an effect.


    It doesn’t seem to be a critical error; you can still write and save posts and pages, and your site looks normal in the frontend.


    I am experiencing the same error – “Failed to load content css: http://URL/wp-admin/admin-ajax.php/?action=dynamic_styles”, in conjunction with featured images not appearing on Timely’s All-in-One Calendar event pages.
    It would be helpful to know if the error is a WP issue, Mantra theme issue or the calendar plugin’s issue.
    Our site is using the Mantra theme with a child theme for custom css. Everything was working correctly until we updated to Mantra 2.6.1 and WP 4.8.

    TIA for any help.


    Oleg Chuvakin
    Power User

    I have the same problem: “Failed to load content css: …/wp-admin/admin-ajax.php/?action=dynamic_styles”.



    I have the same problem: “Failed to load content css: …/wp-admin/admin-ajax.php/?action=dynamic_styles”

    i just upgrade to wordpress 4.8 and use nirvana 1.4.1



    If you use a Child theme of Nirvana, you can no longer put @import url("../nirvana/style.css"); in the style sheet of your child theme. Instead you must use functions.php as described on


    Frank – thank you for your comment.

    For MWVTA’s site I am using Mantra 2.6.1, WP 4.8 and the “wp_enqueue” function in the functions.php file, and we are getting the “Failed to load……” error message like others in this thread. Prior to updating to Mantra 2.6.1 and WP 4.8 everything worked fine.

    I do not get the error on other websites I manage that are also on WP 4.8, using other themes, so it appears to be an issue with Cryout’s themes.

    While this issue might not be a critical error, it is definitely annoying.


    Power User

    Frank, thank you, also, for your comment, where you wrote:

    If you use a Child theme of Nirvana, …

    I don’t believe I used a Child theme, as I’m not sure what a child theme is. I’ll look that up.
    Is there a way to check that and delve more deeply into removing what JeanC said was not “a critical error, [but] it is definitely annoying.”

    Thanks again.

    Oleg Chuvakin
    Power User

    The Tempera theme was updated (I use it). Everything works. No error. Thanks!



    rcburr – From the WP Codex: “A child theme is a theme that inherits the functionality and styling of another theme, called the parent theme. Child themes are the recommended way of modifying an existing theme”.

    Using a child theme to modify a parent theme keeps your changes from being overwritten whenever the parent theme is updated.

    Oleg Chuvakin – I see the Tempera theme was updated yesterday, which included “Fixed TinyMCE editor error on WordPress 4.8”. Hopefully the Mantra theme will be updated soon as well.


    Power User

    Thanks JeanC. The parent child theme concept is a nice idea. These folks have some good explanations:

    If fixes have started, then Nirvana may be soon, too.


    rcburr – You’re welcome. WPBeginner is a good resource for WordPress questions.


    it is caused by

    // Synchronizing the tinymce width with the content width
    add_filter(‘tiny_mce_before_init’, ‘nirvana_dynamic_editor_styles’, 10);
    function nirvana_dynamic_editor_styles($settings){
    $settings[‘content_css’] .= “,”.admin_url(‘admin-ajax.php’) .”/?action=dynamic_styles”;
    return $settings;

    from nirvana/admin/admin-functions.php (in WP4.8 there were changes in TinyMCE AFAIK – perhaps Nirvana need a fix)


    I am getting the same error message, Does Nirvana theme need an update???

    My error code—Failed to load content css:

    Cryout Creations mastermind

    We are aware of this problem with WordPress 4.8. We’ll publish an update to correct it today.

    If you like our creations, help us share by rating them on
    Please check the available documentation and search the forums before starting a topic.

    I think even the update to Nirvana which was resently posted is causing problem in the editor. My background in the editor has changed, text is all messed up with formating it’s become a nightmare


    My backend post and page editor is all wonky too now since the “fix” for the error message.. my page has split to 1/2 the screen! page not loading properly reducing to half the size

    I have included a link so you can see what it is doing… I am only seeing 1/2 of my post.. it all reduces and moves to the left side of the screen.

    I use tempura and this started within the last 24 hours?! It was fine yesterday am…


    Power User

    OnFire, I was unable to see a problem with your site pages. Would the problem be just with the page and post editors?

    P.S., My wife is a quilter. 😎


    I tried to post a link with an image… it doesn’t seem to be working properly.. It is on the editing side so you wouldn’t see it by visiting the site.

    They won’t accept my link to the image of what I see.. I have tried several times and it doesn’t show.

    • This reply was modified 7 years ago by OnFire.
    • This reply was modified 7 years ago by OnFire.
    • This reply was modified 7 years ago by OnFire.
    Cryout Creations mastermind

    Nirvana’s 1.4.2 update includes two changes related to the content editor:

    • a fix for the “Failed to load content CSS” error with WordPress 4.8
    • a revamp for the editor styling which tries to recreate the same appearance of the content as on the frontend into the editor itself (to give a feel about how your content will actually look and fit on the site). This includes the content width and text and background colours.

    If you dislike this second change we’ve also put an option under the theme’s Miscellaneous settings with which the editor styling can be turned off.

    If you like our creations, help us share by rating them on
    Please check the available documentation and search the forums before starting a topic.
    Power User

    Thank you, Zed. That’s good news.


    Zed – will the Mantra theme be updated as well?

    Thank you – JeanC


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