.yanel-GlassPanel{
 background-color: black;
 filter:alpha(opacity=50);-moz-opacity:.50;opacity:.50;
}

.gwt-GlassPanel {

  /* Override glass panel color to be `green`*/ 
  background-color: black !important;

  /* Override glass panel to 10% opacity (= 90% transparency) */
  filter: alpha(opacity = 50) !important; /* IE */
  opacity: 0.5 !important; /* non-IE */

  /*
    NOTE: Please do NOT use either CSS 'width' or 'height' here, as
    this would defeat much of the effort that went into GlassPanel
    in order to get it to work consistently in a variety of
    circumstances. Specifically, please resist the urge to use
    'width/height: 100%' or similar constructs.
  */
}