You cannot target text nodes with CSS. I'm with you; I wish you could... but you can't :(
If you don't wrap the text node in a <span>
like @Jacob suggests, you could instead give the surrounding element padding
as opposed to margin
:
<p id="theParagraph">The text node!</p>
p#theParagraph
{
border: 1px solid red;
padding-bottom: 10px;
}