@namespace url(http://www.w3.org/1999/xhtml);

@-moz-document domain("youtube.com") {
.ad-div, #watch-channel-brand-cap, #side-announcement-box,  .homepage-yellow-block-bot,  .ad300x250, #ad300x250, DIV#chrome-promo, A.chrome-link, iframe, #watch-channel-brand-div, .ad-div homepage-side-block 
{ display: none !important; }
}