Internet Explorer compatibility

[si70]

Morning all. Have come up against browser compatibility issues with a site I have done containing radius and gradient styling in IE. I have been told that by adding the following code to the core and a cutom.css file in the css folder for the template (rt-Quasar) would fix the problem.

<!--[if lt IE 9]>
<?php
$gantry->addStyles(array($gantry->addStyles(array('IE_alternative.css'));
?>
<![endif]-->

In a nutshell it doesn't work. Could anybody tell me the best way to accomplish this specifically in the joomla context. Many thanks in advance. Simon ?