I need background-color for comment - css

Question

I have 2 comments on http://11klassniki.ru/post_ccuz.php?id_ccuz=19. One of them is reply for first comment.
He has
#commentRoot li
{
margin: 7px 0 7px 10px;
}
I tried to give him
background-color:blue;
but this color reflect for all comments. I need to give background-color only for replies.
css
ul
{
list-style-type: none;
width: 700px;
}
#commentRoot li
{
margin: 7px 0 7px 10px;
}
#commentRoot li a
{
margin-left: 500px;
}
#commentRoot li .commentContent
{
border: solid 1px #ccc;
padding: 5px 10px;
border-radius:5px; -moz-border-radius:5px; -webkit-border-radius:5px;
margin: 5px 10px;
}
#commentRoot li h6
{
color: #085991;
}
#commentRoot li h6 span
{
color: #666; font-size: 11px;
margin-left: 20px;
}
#commentRoot li .comment
{
margin-top: 5px;
}
#commentRoot li a.reply
{
font-size: 11px;
}
/* Формочка */
#newComment, .loader {display: none;}
#cancelComment
{
float: right; width: 20px; color: red; cursor: pointer;
}
#newComment input
{
height: 26px; width: 250px; padding: 0 5px ; margin-left: 50px;
border: solid 1px #ccc;
}
#newComment textarea
{
width: 350px; height: 100px; margin-left: 5px;
vertical-align: middle; border: solid 1px #ccc;
}
#newComment button
{
margin-left: 102px; margin-top: 10px;
}

Answer 1

You could do something like (check JSFiddle here)
#commentRoot li .commentContent {
border: none;
padding: 5px 10px;
margin: 5px 10px;
}
#commentRoot li ul li .commentContent {
border: solid 1px #ccc;
padding: 5px 10px;
border-radius: 5px;
-moz-border-radius: 5px;
-webkit-border-radius: 5px;
margin: 5px 10px;
}

Answer 2

you can try use specificity of the elements, like this:
#commentRoot li ul .commentContent {
background-color: blue;
}
Look a demo here: http://jsfiddle.net/LaLc4ryb/