code: function (css, cssText) {
              if (lang.isObject(css) && 'opacity' in css) {
                  css = lang.merge(css,{
                          filter: 'alpha(opacity='+(css.opacity*100)+')'
                        });
                  delete css.opacity;
              }
              return _toCssText(css,cssText);
          }
docs: Wrap IE's toCssText to catch opacity.  The copy/merge is to preserve the input object's integrity, but if float and opacity are set, the input will be copied twice in IE.  Is there a way to avoid this without increasing the byte count?