@SLaks is absolutely correct regarding the error message you're encountering.
To further enhance your understanding, allow me to introduce a more effective method for targeting Internet Explorer:
<!-- paulirish.com/2008/conditional-stylesheets-vs-css-hacks-answer-neither/ -->
<!--[if lt IE 7]><html class="ie6" lang="en"><![endif]-->
<!--[if IE 7 ]><html class="ie7" lang="en"><![endif]-->
<!--[if IE 8]><html class="ie8" lang="en"><![endif]-->
<!--[if IE 9 ]><html class="ie9" lang="en"><![endif]-->
<!--[if IE 10 ]><html class="ie10" lang="en"><![endif]-->
<!--[if !IE ]><!--><html class="non-ie" lang="en"><!--<![endif]-->
The advantage of this approach is that it allows you to adhere to the best practice of utilizing only one stylesheet. You simply need to prefix your target with the corresponding IE class you wish to manipulate.
For instance: .ie6 #target-id
For a more comprehensive explanation, I recommend reading Paul Irish's article:
Conditional stylesheets vs CSS hacks? Answer: Neither!