The code action request is sent from the client to the server to compute commands for a given text document and range. These commands are typically code fixes to either fix problems or to beautify/refactor code. The result of a textDocument/codeAction request is an array of Command literals ...
Of course, if you must validate your CSS (because you want to show your client or you have a boss who doesn’t understand that validation is of minimal importance), then you have some ways to get aroundsomeof the errors produced by the validator. Many people don’t seem to realize this...