discourse/app/views/common/_discourse_stylesheet.html.erb

<%- unless SiteCustomization.override_default_style(session[:preview_style]) %>

  <script type="text/javascript">
    (function() {
      var h = document.getElementsByTagName('html')[0],
          isMobileView = (localStorage && localStorage.mobileView) ? (localStorage.mobileView === 'true') :
              Modernizr.mq("only screen and (max-width: 480px), only screen and (max-device-width: 480px)");

      h.className += (isMobileView ? ' mobile-view' : ' desktop-view');
      Modernizr.load({
        test: isMobileView,
        yep:  <%= stylesheet_filenames(:mobile).inspect.html_safe  %>,
        nope: <%= stylesheet_filenames(:desktop).inspect.html_safe %>,
        complete: function() {
          // CSS file(s) have loaded.
          $(function() {
            setTimeout(function() {
              // Use setTimeout to make this happen in the next event loop.
              // Trying to avoid a FOUC (flash of unstyled content).
              if (isMobileView) {
                $('#custom-mobile-header').show();
              } else {
                $('#custom-desktop-header').show();
              }
              $('#js-app').attr('style', ''); // Show everything.
              $(window).trigger('scroll.discourse-dock'); // Calc header div positions now that they're visible.
            }, 1);
          });
        }
      });
    })();
  </script>

<%- end %>

<noscript>
  <%= stylesheet_link_tag "desktop" %>
</noscript>

<%- if staff? %>
  <%= stylesheet_link_tag "admin"%>
<%-end%>