performance-art.fr/sites/all/modules/contrib/dev/ctools/css/collapsible-div.css

.ctools-collapsible-container .ctools-toggle {
  float: left;
  width: 21px;
  height: 21px;
  cursor: pointer;
  background: url(../images/collapsible-expanded.png) no-repeat 7px 7px;
}

.ctools-collapsible-container .ctools-collapsible-handle {
  display: none;
}

html.js .ctools-collapsible-container .ctools-collapsible-handle {
  display: block;
}

.ctools-collapsible-container .ctools-collapsible-handle {
  cursor: pointer;
}

.ctools-collapsible-container .ctools-toggle-collapsed {
  background-image: url(../images/collapsible-collapsed.png);
}