var GB_DONE = false;
var GB_HEIGHT = 400;
var GB_WIDTH = 400;
function GB_showCenter(caption, url, height, width) {
  GB_HEIGHT = height || 400;
  GB_WIDTH = width || 400;
  if(!GB_DONE) {
    $(document.body).append("<div id='GB_overlay'></div><div id='GB_window'><div id='GB_caption'></div>" + "<img src='_themes/close.gif' alt='Close'/></div>");
    $("#GB_window img").click(GB_hide);
    $("#GB_overlay").click(GB_hide);
    $(window).resize(GB_position);
    GB_DONE = true;
  }
  $("#GB_frame").remove();
  $("#GB_window").append("<iframe id='GB_frame' src='"+url+"'></iframe>");
  $("#GB_caption").html(caption);
  $("#GB_overlay").show();
  GB_position();
  $("#GB_window").show();
}
function GB_hide() {
  $("#GB_window,#GB_overlay").hide();
}
function GB_position() {
  var de = document.documentElement;
  var w = self.innerWidth || (de&&de.clientWidth) || document.body.clientWidth;
  $("#GB_window").css({width:GB_WIDTH+"px",height:GB_HEIGHT+"px",left: ((w - GB_WIDTH)/2)+"px" });
  $("#GB_frame").css("height",GB_HEIGHT - 32 +"px");
}