MediaWiki:Monobook.css

/* edit this file to customize the monobook skin for the entire site */

/******* Hiding .firstHeading, #siteSub, #contentSub on pages in ns:Portal */
body.page-Main_Page #siteSub, 
body.page-Main_Page #contentSub, 
body.page-Main_Page h1.firstHeading {
display: none !important;
}