Because both types of links are exactly the same, they will react to common
CSS declarations the same way.
<a href="
http://www.example.com">External Link</a>
<a href="#bookmark1">Bookmark Link</a>
There's no way to automagically use CSS to style them differently. (Let me
qualify that by saying there may be a way in the newest CSS spec, but it
won't be supported very well.)
You're going to have to create a new class and apply it to one of the link
types. So, assume you want to style the bookmark links you could create a
more specific style for bookmarks and then apply that to any bookmark link.
For example:
<html>
<head>
<style type="text/css">
a:link { color: #008000; }
a:link.bookmark { color: #f00; }
</style>
</head>
<body>
<p><a href="
http://www.example.com">External Link</a></p>
<p><a href="#bookmark1" class="bookmark">Bookmark Link</a></p>
</body>
</html>
Note that you _need_ to combine the a:link.bookmark for it to apply to link
text.