Here is an example of an HTML file that uses a style sheet to modify the <B> tag:
<html>
<style type="text/css">
<!--
B { color: #FF0000; }
-->
</style>
<body>
<p>This is <b>bold</b> text.</p>
</body>
</html>
In this example, every instance of the <b> tag will have the color #FF0000 (red) applied to it, like this:
This is bold text.