My problem solved but not thanks to Yslow 2.0b4 Rated 5 out of 5 stars
My problem solved thanks to Firebug 1.4b7 : i'll explain it , it may be also another's problem : the first problem was that always when I open Yslow with Firebug you have to refresh the page to make Firebug working and Yslow too , but that's not the main problem . The main problem was once i refreshed the page instead of reducing firebug , i closed it , and i have seen that thanks to firebug 1.4b7 release that clearly show an "off" button on the red cross to close : so don"t do it ! Only reduce firebug/Yslow !
Except of that , i think the yslow 2.0b3 release modified on rapidshare proposed below by poblone should have worked great for me too.
To end with glad to see yslow isn't dead and released a 2.0b4 release as others say.:D and good holydays good summer ! Bye .