I have created a child theme from twenty eleven to an rtl website, and since in ie7 things aren't as they should be, I created an ie7.css file and inserted conditional comments to the head.
This is the code:
<link rel="stylesheet" type="text/css" media="all" href="<?php bloginfo( 'stylesheet_url' ); ?>" /> <!--[if lte IE 7]> <link rel="stylesheet" href="<?php bloginfo('template_directory'); ?>/ie7.css" media="screen" type="text/css" /> <![endif]-->
Now something must be wrong in the code becauses the ie7.css file is being completely ignored.