Oi,

Provavelmente um erro de sintaxe.

Eu precisaria ver seu CSS para ajudá-lo com mais precisão.

Mas tente alguns validadores CSS para verificar se o seu CSS não tem erros de sintaxe e, por exemplo, se você usar algum href, verifique se as / estão corretas, se não estiver usando barras invertidas

Exemplo href ="/styles/style.css" em vez de href="styles/style.css"

Hi,

It's probably a syntax error. I would need to see your CSS to help you more precisely. 

But try some CSS validators to check if your CSS has any syntax errors and, for example, if you use any hrefs, check if the / are correct, if you are not using backslashes. 

Example: href ="/styles/style.css" instead of href="styles/style.css"

Hi @Łukasz Kaproń,

The error message simply tells us the browser did not receive a valid CSS file from that URL. 

Instead of: 

• Content-Type: text/css 

the server returned either: 

• an empty response 
• or HTML / an error page 
• or a broken CSS bundle 
• Chrome blocks it due to strict MIME checking.

In Reactive Web apps, App.App.extra.css is auto‑generated by the platform and includes:

• Screen‑level CSS 
• Web Block CSS 
• Theme overrides 
• Custom CSS snippets 

If any CSS fragment is invalid, the platform fails to compile the bundle, and the runtime ends up serving a non‑CSS response at: /App/css/App.App.extra.css

Most common root cause:

• Missing } or ; 
• CSS comments not closed: /* broken comment
• Invalid selectors 
• Using HTML inside CSS 
• Copy‑pasted JS inside 
• Incorrect @import or url() paths inside CSS
• CSS referencing unsupported or blocked resources 
  • example: background: url('http://external-site/font.woff'); 

Once any screen introduces invalid CSS, the shared bundle breaks for the whole app.

Hope this helps.

Cheers,

Saugat