Refused to apply style because its MIME type ('text/html') is not a supported stylesheet MIME type, and strict MIME checking is enabled.

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Posted on by Shaheer Ahmad

2,194 Moderator

Hello,

I am working on a Power Pages website. We seem to encounter this error on every page. I've tried searching for thumbnail.css but couldn't find any documentation regarding it. Its not even mentioned here:
Power Pages: Manage CSS

Can somebody please explain the root & solution of these errors?

Refused to apply style from 'https://<url>/thumbnail.css?1706249049000' because its MIME type ('text/html') is not a supported stylesheet MIME type, and strict MIME checking is enabled.

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Akah Mandela 445 on at

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Try using another browser and see if you face same issue
Check the URL of the CSS file to ensure its accessible via the url. you can do that by copying 'https://<url>/thumbnail.css?1706249049000' and pasting in another tab in the browser, this should return plain CSS.

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Shaheer Ahmad 2,194 Moderator on at

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I've tried pasting the URL in browser. It's accessible but it's returning a kind of a bit messed up version of my home page.

Also these errors appear in the console when i accessed the thumbnail.css url

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Lucas001 2,529 Super User 2026 Season 1 on at

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Hi @ShaheerAhmad,

did you encounter the error lately and has been fine before?
Also is the page already in production? I had similar issue a long time ago and only my dev page was effected.
Somehow it healed itself after some days as Microsoft is continuously working in the backend.

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Shaheer Ahmad 2,194 Moderator on at

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I am not sure if this error was existing before, I only got to know about it when we sent the portal over for testing.

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Shaheer Ahmad 2,194 Moderator on at

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I now downloaded the thumbnail.css from portal's web file and stored it as a local backup. After opening the CSS file, I noticed HTML/JS content from my home screen. I created a copy and removed all the HTML and JS and left the CSS as is (Although it was the CSS from my portal's home page). and uploaded the file. Now the error's gone. Not sure if it will effect any functionality. If it does, I'll add a new reply to this thread. Meanwhile everything is working fine.

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