<div id="sidebar">
<h3 class="sideheading">About This Site</h3>
<p>This is my site.</p>
<h3 class="sideheading">My Links</h3>
<ul class="sidelinks">
<li class="link"><a href="archives.html">Archives</a></li>
<li class="link"><a href="about.html">About Me</a></li>
</ul>
</div>

.sideheading {
font-family: Georgia, serif;
color: #c63;
border-bottom: 1px solid #ccc;
}
.sidelinks {
list-style-type: none;
}
.link {
font-weight: bold;
}

<div id="sidebar">
<h3>About This Site</h3>
<p>This is my site.</p>
<h3>My Links</h3>
<ul>
<li><a href="archives.html">Archives</a></li>
<li><a href="about.html">About Me</a></li>
</ul>
</div>

#sidebar h3 {
font-family: Georgia, serif;
color: #c63;
border-bottom: 1px solid #ccc;
}

#sidebar ul {
list-style-type: none;
}

#sidebar li {
font-weight: bold;
}

h3 {
font-family: Georgia, serif; /* All h3s to be serif */
}
#content h3 {
color: purple;
}
#sidebar h3 {
color: orange;
}

<div id="sidebar">
<h3>About This Site</h3>
<p>This is my site.</p>
<h3>My Links</h3>
<ul>
<li><a href="archives.html" class="red">Archives</a></li>
<li><a href="about.html" class="red">About Me</a></li>
</ul>
</div>

a:link.red {
color: red;
}

#sidebar li a:link {
color: red;
}