IE8 is detecting the pages as mobile media
As you haven't provided any information this is a complete guess, based on the assumption that you're using the Omega 3 theme with respond.js.

There's a known issue with IE8, respond.js and CSS aggregation. To fix it, you can implement hook_css_alter() in your theme like so:

function MYTHEME_css_alter(&amp;$css) {
  // Enable respond.js to work with Omega.
  foreach ($css as $key =&gt; $value) {
    if (preg_match('/^ie::(\S*)/', $key)) {
      unset($css[$key]);
    }
    else {
      $css[$key]['browsers']['IE'] = TRUE;
    }
  }
}