In my react project i use tailwind css. i have installed every package I need. When I run the project, it runs without errors. But, in every jsx file, the first line has an error. it says Unknown word (CssSyntaxError)

I want that when the page is loaded, the variable will receive a value from local storage, if it does not exist from the browser settings. But when she does this, the class in html does not change. How to fix it?