I' using the Omega theme (http://drupal.org/project/omega) and it doesn't support responsive designs in IE8 and below that Omega uses.
Figured it out! I installed the respondjs module (http://drupal.org/project/respondjs) and had to make a modification to the template.php. Check out http://drupal.org/node/1388898. It looks like the IE specific CSS file(s) are preventing the respond.js file to not work. I removed the IE specific stylesheets and changed ['browsers']['IE'] from gte IE 9 to TRUE. This seems to work for me. I added the following code to my omega subthemes template.php file.
<?php
function omega_subtheme_css_alter(&$css) {
foreach ($css as $key => $value) {
if (preg_match('/^ie::(\S*)/', $key)) {
unset($css[$key]);
} else {
$css[$key]['browsers']['IE'] = TRUE;
}
}
}
?>