materio-base-d7/sites/all/modules/contrib/editor/wysiwyg/plugins/break/break.css

.wysiwyg-break {
  display: block;
  border: 0;
  border-top: 1px dotted #ccc;
  margin-top: 1em;
  width: 100%;
  height: 12px;
  background: transparent url(images/breaktext.gif) no-repeat center top;
}