After editing the code snippet below...
<div id="rt-utility"><div class="rt-block fp-roksprocket-grids-utility title5 jmoddiv">
I applied the changes in my custom.css file like this:
#rt-utility .rt-block {CODE HERE}
However, when attempting to modify...
<div id="rt-sideslider-overlay"><header id="rt-header-surround">
using
#rt-sideslider-overlay .header-rt-header-surround {CODE HERE}
The modification did not take effect. Could this be due to it being a header id instead of a div id??