About the instrution to use body.page-Main_Page.action-view h1.firstHeading, body.page-Main_Page.action-submit h1.firstHeading { display: none; }
, it is wrong.
My Mediawiki <body> have only "invalid page" classes: sitedir-ltr
, ..., mw-special-Badtitle, page-Especial_Título_inválido, rootpage-Especial_Título_inválido
.
There are no replacement for "page-Main_Page" as stated by instruction.