If you open mistresses.html in a text editor (such as Fraise on Mac OS X), you’ll see that it references a file called “reviews.css”:
<link rel="StyleSheet" href="reviews.css" type="text/css" media="all" />
This is how you include a stylesheet in your web page. Often, you’ll have several web pages all referencing the same style sheet. This way, if we have hundreds of book reviews, we can change the appearance of all of our reviews by changing a single style sheet.
In this case, that style sheet is called “reviews.css” and is in the same folder as “mistresses.html”—or it will be, once we create it.