#mistake1 {
  background-image: url(overlay.png);
  position: absolute;
  margin: auto;
  top:  0;
  left: 0;
  z-index: 100;
  width:  100%;
}

* html #mistake1 {
  background-image: none;
} 

#m_window1 {
  position: absolute;
  overflow: auto;
  width:326px;
  height: 288px;
  z-index: 150;
}

#m_frame1 {
  border: 0; 
  overflow: auto;
  width: 100%;
  height: 100%;
}