If this paragraph is green and has a border (for you colorblind folks), the non-IE6 stylesheet loaded.
If this paragraph is red and italic, the IE6-only stylesheet loaded.
The following method was used:
<![if ! lte IE 6]><link rel="stylesheet" href="green.css" media="screen, projection"><![endif]> <!--[if lte IE 6]><link rel="stylesheet" href="red.css" media="screen, projection"><![endif]-->
Note that this uses Microsoft's lesser-known "downlevel revealed" conditional comments. These do not pass validation, but work correctly. I personally do not care that the validator whines about the unknown
<!> tag, but some may. However, the other method does not really solve this issue.
(“Downlevel revealed” conditional comments treat non-IE browsers as “downlevel”, ironically enough. The name comes from the fact that they are also revealed in IE4(?) and lower.)
This works as a technique to include CSS, JS, and other content.