Here is the correct format of the comment:
<!--[if IE ]>
Special instructions for IE here
<![endif]-->
here is a NOT IE comment:
<!--[if !IE ]>
According to the conditional comment this is not IE
<![endif]-->
source: http://www.quirksmode.org/css/condcom.html
edit: just noticed that their 'not' example is wrong. i have corrected it.