When you place content inside a conditional comment, it will only be recognized by specific browsers. This allows you to include multiple link-tags within one conditional comment; however, in this scenario, all tags will be read by IE versions 5,6,7, and 8. If you require separate stylesheets for each version, you must use individual conditional comments for each.
For further insights, check out the following blog post:
This technique can assist in streamlining your use of conditional comments.
edit:
Here's a demonstration:
HTML:
<!--[if IE]><html class="ie"><![endif]-->
<!--[if !IE]><!--><html><!--<![endif]-->
<head></head>
<body>
<h1>Foo!</h1>
</body>
</html>
CSS:
h1{
font-size:2em;
}
.ie h1{
/* This rule applies exclusively to Internet Explorers - across all versions */
font-size:1.5em;
}