An element inherits the properties of its parent element unless otherwise specified. So, this overdeclared example:
<style type="text/css">
body{font:1em arial,helvetica,sans-serif;}
p.normal1em{font:1em arial,helvetica,sans-serif;} /* extra declaration */
div {font:1em arial,helvetica,sans-serif;} /* another one */
#content em{color:red;} /* em for emphasis color */
#content em.ed {color:#00331a;}
</style></head><body>
<div id="content">
<p class="normal1em">Normal text here, brute forced from the p rule.
<em class="ed">Editors note: Note that inherited CSS can provide
this approach more efficiently.</em></p>
</div> </body>becomes this, by moving the common font declaration up into the body rule and eliminating the p rule and div rules which are implied by inheritance:
<style type="text/css">
<!--
body{font:1em arial,helvetica,sans-serif;}
#content em{color:red;} /* em for emphasis color */
#content em.ed {color:#00331a;}
--></style></head><body>
<div id="content">
<p>Normal text here, inherited from the body rule.
<em class="ed">Editors note: Note the inherited style
that CSS provides with this approach...</em></p>
</div> </body>The child div and paragraph elements now inherit the same font size and family from the body rule.