What do you think about Render-blocking?

The browser halts downloading the remaining resources when it comes across a resource that prevents rendering until these crucial files are processed. The entire rendering process is suspended in the interim.

By default, CSS is considered a resource that prevents the browser from rendering any processed content until the CSSOM has been created. Use media types and queries to unblock rendering, make your CSS as concise as possible, and deliver it as rapidly as you can.