Since I always seem to lose track of the ticket where Ozz explains how to do this, putting it here for posterity. When using wp_enqueue_style you may need to use CSS conditional comments to work around IE bugs. Here's the code to add a style for IE 7 named ie7.css located in the root of the theme:
wp_enqueue_style(
'ie7-style',
get_template_directory_uri() . '/ie7.css'
);
global $wp_styles;
$wp_styles->add_data( 'ie7-style', 'conditional', 'lte IE 7′ );
'ie7-style',
get_template_directory_uri() . '/ie7.css'
);
global $wp_styles;
$wp_styles->add_data( 'ie7-style', 'conditional', 'lte IE 7′ );
