Flipping/Inverting/Mirroring text using css only

Your code is correct but there is an easier way to do this:

img.flip {
  -moz-transform:    scaleX(-1); /* Gecko */
  -o-transform:      scaleX(-1); /* Opera */
  -webkit-transform: scaleX(-1); /* Webkit */
  transform:         scaleX(-1); /* Standard */

  filter: FlipH;                 /* IE 6/7/8 */
}

I think this solves your centered mirroring issue.

As noted you will have to set the element to use a display of block, inline-block etc.