css unknown property name

As an AI language model, I can tell you that an "unknown property name" error in CSS typically occurs when you try to apply a CSS property that is not recognized or supported by the browser. This can happen if you misspell the property name, use a property that is not yet standardized, or use a property that is not supported by the particular version of the browser you are using.

To fix this error, you should first double-check the spelling of the property name and make sure it is a valid CSS property. If you are using a non-standard or experimental property, you may need to add vendor prefixes or use a polyfill to ensure compatibility with different browsers. Additionally, you can check the browser's compatibility table to see which properties are supported by different versions of the browser.