hide site title, desc

1. I’d like to hide the site title and description from displaying on the site.

Here’s the code in WP admin > GDF Options > Quick code:

#header{
margin: 0 auto;
}

#site-title, #site-description {
display: none;
}

The above code isn’t working at all — I still see the site title displaying above the banner image. Any ideas on how to fix code?