In my content/themes/default/views/layouts/default.html.erb file I have these set:
<%= stylesheet_link_tag 'default' %>
<%= javascript_include_tag 'default' %>
those files are in content/themes/default/assets/stylesheets and javascripts respectively. Yet in my browser my site throws a 404 on both /stylesheets/default.css and /javascripts/default.js