CSS Style within a style?

Is it possible to have a style within a style?

For example, something like this:

#content
{
text-align: center;
border-style:solid;
border-width:10px;
border-color: #121212;

     h1
     {
       font-family: arial;
     }

}

What I am actually trying to do is have the header font as arial only inside the content div.