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Troubleshooting Common Simple Custom CSS and JS Plugin Conflicts

43 threads Sep 16, 2025 Plugin → Simple custom css and js

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If you use the Simple Custom CSS and JS plugin, you might occasionally run into issues where it doesn't seem to work, causes errors, or conflicts with other parts of your site. Based on common support queries, this guide will help you diagnose and resolve the most frequent problems.

1. Editor Issues (White Overlay, Missing Fields, Small Window)

A very common problem is a white overlay covering the code editor, making it impossible to write or edit code. This is almost always caused by a conflict with another plugin or your theme that also uses the CodeMirror editor library.

How to troubleshoot:

  • Deactivate other plugins: Temporarily deactivate all other plugins. If the editor works again, reactivate your plugins one by one to identify the culprit. Common conflicting plugins include other code editors, file managers, page builders, or optimization tools.
  • Switch themes: Temporarily switch to a default WordPress theme like Twenty Twenty-One. If the editor works, the issue is with your theme.
  • Check for updates: Ensure all plugins and your theme are updated. The Simple Custom CSS and JS team has resolved many such conflicts in past updates.

2. Custom Code Not Working After a WordPress Update

After a core WordPress update, you might find your JavaScript code has stopped working, often throwing errors like TypeError: $ is not a function in the browser's console.

Why this happens: WordPress has moved towards using JavaScript in a more compatible way, which can break code that relies on the traditional $ shorthand for jQuery.

The solution: You need to wrap your code to properly reference jQuery. Replace any code starting with $(document).ready(function() { with the following structure:

jQuery(document).ready(function($) {
    // Your existing code here. You can use the $ inside this function.
    $(".your-selector").doSomething();
});

3. 403 Forbidden Error When Saving Code

Clicking the save button and getting a "403 Forbidden" error is a server-level security issue, not a plugin bug.

Why this happens: Your web host's mod_security firewall is likely triggered by the content of your code (often JavaScript or HTML). It blocks the request to save it, interpreting it as a potential threat.

How to resolve it: Contact your hosting provider's support. Explain that you are getting a 403 error when trying to save custom code in your WordPress admin. Ask them if they can check the mod_security rules and either whitelist the request or adjust the rule that is being triggered.

4. Plugin Could Not Be Activated (Fatal Error)

Attempting to activate the plugin results in a fatal error, often mentioning a line in admin-screens.php.

Why this happens: Your server is running a very old and unsupported version of PHP (e.g., 5.2 or 5.3). The plugin requires a newer version of PHP to function.

The fix: You must update the PHP version for your WordPress site. Most hosting providers allow you to do this from your hosting control panel (e.g., cPanel). Contact your host for assistance if needed. Aim for at least PHP 7.4, though PHP 8.x is recommended.

5. General Debugging Steps for Other Issues

For other problems—like codes not appearing, redirects on save, or strange behavior—follow this basic troubleshooting procedure:

  1. Conflict Test: Deactivate all other plugins except Simple Custom CSS and JS. See if the problem persists.
  2. If the problem is resolved, reactivate your plugins one by one to identify which one causes the conflict.
  3. Theme Test: If deactivating plugins doesn't help, temporarily switch to a default WordPress theme (e.g., Twenty Twenty-Four) to rule out a theme conflict.
  4. Check Error Logs: For fatal errors or 500 internal server errors, enable WordPress debugging or check your hosting provider's error logs. The logs will provide the specific error message needed to find a solution.

By methodically working through these steps, you can usually identify and resolve the conflict causing issues with the Simple Custom CSS and JS plugin.

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