function showOverlay(message) {
  
  // Erstellt ein Konstrukt ähnlich diesem:
  //
	//	<div id="overlay"></div>
	//	<div id="overlay_body">
  //	  <div id="overlay_message">
  //  	   <p>...</p>
	//	  </div>
	//	</div>
  
  var objBody = document.getElementsByTagName("body").item(0);
	
	var objOverlay = document.createElement("div");
	objOverlay.setAttribute('id','overlay');
	objBody.appendChild(objOverlay);
	
	var objOverlayBody = document.createElement("div");
	objOverlayBody.setAttribute('id','overlay_body');
	objBody.appendChild(objOverlayBody);
	
	var objOverlayMessage = document.createElement("div");
	objOverlayMessage.setAttribute('id','overlay_message');
	objOverlayBody.appendChild(objOverlayMessage);
	
	var objParagraphMessage = document.createElement("p");
	objParagraphMessage.setAttribute('id','overlay_paragraph');
	
	// objParagraphMessage.innerHTML = "<img src=\"includes/inc_plugins/overlay/upload.gif\" /><br />" + message;
	objParagraphMessage.innerHTML = message;
	
	objOverlayMessage.appendChild(objParagraphMessage);
	
	
	// einige Attribute für die Elemente setzen
  var pageSize = getPageSize();
  document.getElementById("overlay").style.height = pageSize[1] + "px";
  document.getElementById("overlay_body").style.top = (pageSize[1] - (pageSize[3] / 2)) + "px";
};

//
// getPageSize()
// Returns array with page width, height and window width, height
// Core code from - quirksmode.org
// Edit for Firefox by pHaez
//
function getPageSize() {
	
	var xScroll, yScroll;
	
	if (window.innerHeight && window.scrollMaxY) {	
		xScroll = document.body.scrollWidth;
		yScroll = window.innerHeight + window.scrollMaxY;
	} else if (document.body.scrollHeight > document.body.offsetHeight){ // all but Explorer Mac
		xScroll = document.body.scrollWidth;
		yScroll = document.body.scrollHeight;
	} else { // Explorer Mac...would also work in Explorer 6 Strict, Mozilla and Safari
		xScroll = document.body.offsetWidth;
		yScroll = document.body.offsetHeight;
	}
	
	var windowWidth, windowHeight;
	if (self.innerHeight) {	// all except Explorer
		windowWidth = self.innerWidth;
		windowHeight = self.innerHeight;
	} else if (document.documentElement && document.documentElement.clientHeight) { // Explorer 6 Strict Mode
		windowWidth = document.documentElement.clientWidth;
		windowHeight = document.documentElement.clientHeight;
	} else if (document.body) { // other Explorers
		windowWidth = document.body.clientWidth;
		windowHeight = document.body.clientHeight;
	}	
	
	// for small pages with total height less then height of the viewport
	if(yScroll < windowHeight){
		pageHeight = windowHeight;
	} else { 
		pageHeight = yScroll;
	}

	// for small pages with total width less then width of the viewport
	if(xScroll < windowWidth){	
		pageWidth = windowWidth;
	} else {
		pageWidth = xScroll;
	}

  newArrayPageSize = new Array(pageWidth,pageHeight,windowWidth,windowHeight) 
	return newArrayPageSize;
}