Another tremendously powerful trick you can use with CSS is to specify subclasses and to constrain formatting styles to a subset of your tags. For example, imagine a Web page like this: <div class=”special”> This is a special block and bold words should appear differently than they do in regular text.</div> <p> And this, by contrast, is regular bold text, with a little italics tossed in for luck and an example of italics within bold. </p> To specify that only the bold tags within the class special should have a particular style, use the format class class (in the example below, notice that the b i sequence changes italics within bold sequences only): <style type=”text/css”> .special b { color: green; font-size: 125%; } b i { background-color: yellow; } b,i { font-weight: bold; color: blue; } </style> Look closely to see what’s specified here. Two lines contain a pair of selectors separated by a space; on the third line, the selectors are separated by a comma. On the two lines in which a space separates the selectors, the second selector is affected only when it falls within the first selector. In other words, bold text is green only when the is used within a class=”special” block, and the background color is yellow only when the is used within a tag. In the last of the three CSS lines, I employ a shorthand to specify that both bold tags and italic tags should be in bold with blue text. It’s the same as if I had used b { . } and i { }.