Hi - The code suggested in the current version of this page:
body.mainpage.action-view h1.firstHeading, body.mainpage.action-submit h1.firstHeading { display: none; }
didn't work for me, even though I have the latest version of MediaWiki and haven't futzed around with the pages.
Now I was googling around and I found a post from a 2007 edit of this page which provides the following code to be pasted into the Mediawiki:Common.css:
body.page-Main_Page h1.firstHeading { display: none; }
This has worked for me. I'm no computer whiz so I haven't updated the article, but I thought I'd mention it.