Hi there Joseph Witchard,
I think that a simple example would be the best way to explain how a conditional comment works.
In the example below, you will see that the div id="foo" has its color set to firstly to green and secondly to red.
The methodology of CSS means that second rule will overide the first and set the color to red.
This same principle applies to the conditional comment.
IE reads the color as blue and this overides the red.
Of course, for the conditional comment to be effective it must follow rather than precede the original stylesheet.
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01//EN"
<meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1">
This text will colored red unless your browser is IE.
If that is the case then it will be blue.