firebug_lite.html.erb

<% if request.env["HTTP_USER_AGENT"] =~ /MSIE/ && Rails.env == "development" %>
  <div style="position:absolute; left: 0; top: 0; background-color: #ffc; padding: 4px 10px;">
    <a href="javascript:var firebug=document.createElement('script');firebug.setAttribute('src','http://getfirebug.com/releases/lite/1.2/firebug-lite-compressed.js');document.body.appendChild(firebug);(function(){if(window.firebug.version){firebug.init();}else{setTimeout(arguments.callee);}})();void(firebug);">Firebug</a>
  </div>
<% end %>