Probably the easy way to target any version of Internet Explorer (or all) is to use conditional comments. They are supported only by IE, so a perfect fit if you want to display a message to only this browser. You could also use CSS filters or hacks, but to get the most benefit, I still think conditional comments are the way to go.

You would write a comment like so to target any version of IE:

<!--[if IE]>
<p>You are using Internet Explorer.</p>
<![endif]-->

There's a lot more you can do with conditional comments. See the Wikipedia article linked below.
en.wikipedia.org