_linkNode = function(url, win, attributes) {
        var o = {
            id: Y.guid(),
            type: TYPE_CSS,
            rel: STYLESHEET,
            href: url
        };
        if (attributes) {
            Y.mix(o, attributes);
        }
        return _node('link', o, win);
    }
Generates a link node
@method _linkNode
@param {string} url the url for the css file.
@param {Window} win optional window to create the node in.
@param {object} attributes optional attributes collection to apply to the
new node.
@return {HTMLElement} the generated node.
@private