img {
  -webkit-user-drag: none;  /* Safari and Chrome */
  -khtml-user-drag: none;   /* Konqueror HTML */
  -moz-user-drag: none;     /* Firefox */
  -o-user-drag: none;       /* Opera */
  user-drag: none;          /* Standard */
  
  /* Optional: Prevents text/element selection highlighting around the image */
  -webkit-user-select: none;
  -moz-user-select: none;
  -ms-user-select: none;
  user-select: none;
}