You mentioned that I must identify the different page “heads” that I want to optimize. But this is the trouble. The WordPress uses the SAME head for all pages. The file header.php.
As WordPress uses the same head for all, when I made the critical css, this css will be of my homepage, main page. If I open the “Contact” page the user will download the critical css the “above the fold” of homepage/main page and after will download the css of “contact” page.
Yeah, this is a complex subject to work, but I’ll find it more deeply, study the plugins code that do this and learn how it works from start to finish.
Thank’s a lot for you reply.
I really liked the links you sent. I will read them all carefully.