If you write:

YUI({combine:true}).use('console','node',function(Y){

  var url = Y.Node.one('link[id]').getAttribute('href'),

      con = new Y.Console();

  con.render();

  Y.log(url);

});

You Will Get External Style Combo Url in Head Element:
http://yui.yahooapis.com/combo?3.1.0pr1/build/widget/assets/skins/sam/widget.css&3.1.0pr1/build/console/assets/skins/sam/console.css&

& is in the tail of the url, it is out of place.

demo is http://dancewithnet.com/lab/yui/bug/3.1.0pr1/combo-bug/

I simply fixed the bug in loader.js

   //fixed combo bug

   if(url.slice(-3) ==='.js' || url.slice(-4) === '.css'){

       url += '&';

   }


url += frag;

/*

   if (i < (len - 1)) {

       url += '&';

   }

   */

demo is http://dancewithnet.com/lab/yui/bug/3.1.0pr1/combo-bug/fixed.html