CSS on Post pages only

Hello,

I am trying to target only post pages with CSS, I want to give each post page a Top margin of 120px or so, I am trying
.single #container {top: 120px !important;}
.single #container {margin-top: 120px !important;}

neither work

You can see here I need to push the post pages lower so they are not under the menu
http://aaa.greaterthanthesum.com/network-maps-family-trees/

Thanks