chrome/renderer/resources/plugin_placeholders.css

body {
  font-family: sans-serif;
  margin: 0;
  overflow: hidden;
  text-align: center;
  -webkit-user-select: none;
}

h1 {
  font-size: 10pt;
  font-weight: normal;
  padding: 0pt 10pt;
  visibility: hidden;
}

#outer:hover h1, #outer:hover #close {
  visibility: visible;
}

p {
  font-size: 8pt;
  padding: 0pt 14pt;
}

#outer {
  border: 1px black solid;
  box-sizing: border-box;
  height: 100%;
  position: absolute;
  width: 100%;
}

#inner {
  position: relative;
  top: 50%;
  margin-top: -70px;
}

#close {
  visibility: hidden;
  cursor: pointer;
  position: absolute;
  right: 3px;
  top: 3px;
  height: 14px;
  width: 14px;
  background-image: url("../../../ui/resources/close_bar.png");
  background-position: right top;
  background-repeat: no-repeat;
}

#close:hover {
  background-image: url("../../../ui/resources/close_bar_h.png");
}

#close:active {
  background-image: url("../../../ui/resources/close_bar_p.png");
}