New Header Image Issue

Hello - I am trying to insert a new header image (on my site, www.thelyonsshare.org) and am inserting this code in style.css of my child theme: #header #mainmenu { margin-top: 0; } #header { background: url('http://www.thelyonsshare.org/wp-content/uploads/2013/04/Lyons_Share_Wellness_Header_High[1].png) left bottom repeat-x; } The first part was initially there to reduce margin size, but even when I delete that, I still don't see my image. Can you help me fix the code? Also, what code will I need to remove the existing title and logo (I assume that when I insert my image, you might see the existing title and logo on top of the image)? Thank you so much for your help! Megan