code: function(styleSheet, selector, cssText) {
              var result,
                  ruleSet = styleSheet.cssRules || styleSheet.rules,
                  index = ruleSet.length;
  
              if (styleSheet.insertRule) {
                  styleSheet.insertRule(selector + '{' + cssText + '}', index);
              } else {
                  styleSheet.addRule(selector, cssText||' ');
              }
              CSS.cacheRule(result = ruleSet[index], styleSheet);
              return result;
          }
docs: Creates a rule.
  @param {CSSStyleSheet} styleSheet The StyleSheet to create the rule in as returned from {@link #createStyleSheet}.
  @param {String} selector The selector to target the rule.
  @param {String} property The cssText specification eg `"color:red;font-weight:bold;text-decoration:underline"`
  @return {CSSStyleRule} The created rule