Title: Failed to execute ‘insertRule’ on ‘CSSStyleSheet’: Cannot access StyleSheet Last modified: October 3, 2018 --- # Failed to execute ‘insertRule’ on ‘CSSStyleSheet’: Cannot access StyleSheet * Resolved [ColinD](https://wordpress.org/support/users/colind/) * (@colind) * [7 years, 8 months ago](https://wordpress.org/support/topic/failed-to-execute-insertrule-on-cssstylesheet-cannot-access-stylesheet/) * Our site is hosted on WP Engine and autoptimize worked as expected on dev and staging but when I activated it on production (with WP Engine caching and CDN) I got the following error in the console: Failed to execute ‘insertRule’ on ‘ CSSStyleSheet’: Cannot access StyleSheet to insertRule Unchecking “optimize CSS Code” eliminates the error. * Any advice on how to further diagnose and correct the issue would be greatly appreciated. * The page I need help with: _[[log in](https://login.wordpress.org/?redirect_to=https%3A%2F%2Fwordpress.org%2Fsupport%2Ftopic%2Ffailed-to-execute-insertrule-on-cssstylesheet-cannot-access-stylesheet%2F%3Foutput_format%3Dmd&locale=en_US) to see the link]_ Viewing 8 replies - 1 through 8 (of 8 total) * Plugin Author [Optimizing Matters](https://wordpress.org/support/users/optimizingmatters/) * (@optimizingmatters) * [7 years, 8 months ago](https://wordpress.org/support/topic/failed-to-execute-insertrule-on-cssstylesheet-cannot-access-stylesheet/#post-10748357) * in what browser do you get that error/ warning ColinD? and what are/ were your CSS optimization settings? * Thread Starter [ColinD](https://wordpress.org/support/users/colind/) * (@colind) * [7 years, 8 months ago](https://wordpress.org/support/topic/failed-to-execute-insertrule-on-cssstylesheet-cannot-access-stylesheet/#post-10750398) * Chrome 69, Mac OS Mojave * I played with all the settings options before posting. If I check “Optimize CSS” on the first tab and leave everything as-is on the extra tab (google fonts: leave as is, optimize images: unchecked, remove emojis: unchecked, remove query string: unchecked) The error is present. If I try any of the extras it doesn’t change the error. * Plugin Author [Optimizing Matters](https://wordpress.org/support/users/optimizingmatters/) * (@optimizingmatters) * [7 years, 8 months ago](https://wordpress.org/support/topic/failed-to-execute-insertrule-on-cssstylesheet-cannot-access-stylesheet/#post-10750454) * OK, instead of diving in to settings; I’m pretty sure you have a staging site, no? can we enable CSS opt. there so we (I) can see what happens? * Thread Starter [ColinD](https://wordpress.org/support/users/colind/) * (@colind) * [7 years, 8 months ago](https://wordpress.org/support/topic/failed-to-execute-insertrule-on-cssstylesheet-cannot-access-stylesheet/#post-10750554) * Sure. It works as expected on staging and dev. It’s on WP Engine hosting. My guess is that it is somehow related to the WP Engine production environment’s cache and/or CDN. How can I share access info to the staging site with you? * Thanks for you assistance * Plugin Author [Optimizing Matters](https://wordpress.org/support/users/optimizingmatters/) * (@optimizingmatters) * [7 years, 8 months ago](https://wordpress.org/support/topic/failed-to-execute-insertrule-on-cssstylesheet-cannot-access-stylesheet/#post-10750572) * you can mail me at futtta-at-gmail-dot-com 🙂 * Plugin Author [Optimizing Matters](https://wordpress.org/support/users/optimizingmatters/) * (@optimizingmatters) * [7 years, 8 months ago](https://wordpress.org/support/topic/failed-to-execute-insertrule-on-cssstylesheet-cannot-access-stylesheet/#post-10750871) * OK, good and bad news; -> the bad is that i don’t know why this would not work on the live site while it does work on dev/stating (Autoptimize does not use ` insertRule`) -> there are multiple references to this JS error and the consensus seems to be it is better to have JS add a new stylesheet instead of adding rules to existing ones (see for example [https://github.com/sampotts/rangetouch/issues/12](https://github.com/sampotts/rangetouch/issues/12))- > the good is that I was able to find the (js-)code that is doing the `insertRule`; it’s in `wp-content/themes/userzoom2017/js/scripts.js`, so you might want your devs to look into that * hope this helps, frank * Thread Starter [ColinD](https://wordpress.org/support/users/colind/) * (@colind) * [7 years, 8 months ago](https://wordpress.org/support/topic/failed-to-execute-insertrule-on-cssstylesheet-cannot-access-stylesheet/#post-10753927) * Thanks so much for digging into this for me. I’ve fixed up my code. * Plugin Author [Optimizing Matters](https://wordpress.org/support/users/optimizingmatters/) * (@optimizingmatters) * [7 years, 8 months ago](https://wordpress.org/support/topic/failed-to-execute-insertrule-on-cssstylesheet-cannot-access-stylesheet/#post-10754107) * you’re welcome Colin, feel free to [leave a review of the plugin and support here](https://wordpress.org/support/plugin/autoptimize/reviews/#new-post)! 🙂 * enjoy the weekend! frank Viewing 8 replies - 1 through 8 (of 8 total) The topic ‘Failed to execute ‘insertRule’ on ‘CSSStyleSheet’: Cannot access StyleSheet’ is closed to new replies. * ![](https://ps.w.org/autoptimize/assets/icon-256X256.png?rev=2211608) * [Autoptimize](https://wordpress.org/plugins/autoptimize/) * [Frequently Asked Questions](https://wordpress.org/plugins/autoptimize/#faq) * [Support Threads](https://wordpress.org/support/plugin/autoptimize/) * [Active Topics](https://wordpress.org/support/plugin/autoptimize/active/) * [Unresolved Topics](https://wordpress.org/support/plugin/autoptimize/unresolved/) * [Reviews](https://wordpress.org/support/plugin/autoptimize/reviews/) * 8 replies * 2 participants * Last reply from: [Optimizing Matters](https://wordpress.org/support/users/optimizingmatters/) * Last activity: [7 years, 8 months ago](https://wordpress.org/support/topic/failed-to-execute-insertrule-on-cssstylesheet-cannot-access-stylesheet/#post-10754107) * Status: resolved