function addMarker(lonlat, popupContentHTML, closeBox, overflow) {
	 var size = new OpenLayers.Size(20,14);
	 var offset = new OpenLayers.Pixel(-(size.w/2), -size.h);
	 var icon = new OpenLayers.Icon('http://wiki.christian-willmes.de/extensions/usermap/cmIcon.png',size,offset);

    var feature = new OpenLayers.Feature(markers, lonlat); 
    feature.closeBox = closeBox;
    feature.popupClass = OpenLayers.Class(OpenLayers.Popup.AnchoredBubble, {
            'autoSize': true,
            'minSize': new OpenLayers.Size(280,120),
            'panMapIfOutOfView' : true
        });
    feature.data.popupContentHTML = popupContentHTML;
    feature.data.overflow = (overflow) ? 'auto' : 'hidden';
    feature.data.icon = icon;
                        
    var marker = feature.createMarker();
    var markerClick = function (evt) {
          if (this.popup == null) {
                this.popup = this.createPopup(this.closeBox);
                cmac2map.addPopup(this.popup);
                 this.popup.show();
          } else {
                this.popup.toggle();
          }
            currentPopup = this.popup;
            OpenLayers.Event.stop(evt);
          };
          marker.events.register('mousedown', feature, markerClick);
          markers.addMarker(marker);
	}
	var cmac2map =  new OpenLayers.Map ('cmac2map', {
				maxExtent: new OpenLayers.Bounds(-20037508.34,-20037508.34,20037508.34,20037508.34),
							maxResolution: 156543.0399,
				units: 'm',
				projection: new OpenLayers.Projection("EPSG:900913"),
				displayProjection: new OpenLayers.Projection("EPSG:4326")
			} );
		
    //mapnik
	var mapnik = new OpenLayers.Layer.OSM.Mapnik("Mapnik");	
	//TilesAtHome
	var tah = new OpenLayers.Layer.OSM.Osmarender("Osmarender");
	//CycleMap
	var CM = new OpenLayers.Layer.OSM.CycleMap("CycleMap");
	//Metacarta OpenLayers WMS     
    var ol_wms = new OpenLayers.Layer.WMS( "OpenLayers WMS",
        "http://labs.metacarta.com/wms/vmap0",
        {layers: 'basic'});
 cmac2map.addLayers([tah, CM, mapnik, ol_wms]); 	var center = new OpenLayers.LonLat(0, 0).transform(new OpenLayers.Projection("EPSG:4326"), cmac2map.getProjectionObject());
	cmac2map.setCenter(center, 2);
	cmac2map.addControl( new OpenLayers.Control.LayerSwitcher() );      
	var markers = new OpenLayers.Layer.Markers('Courses');
	
	lonlat = new OpenLayers.LonLat(6.92895, 50.92819).transform(new OpenLayers.Projection("EPSG:4326"), cmac2map.getProjectionObject());
	popupContentHTML = '<b>Course:</b> testCourse</a> <br/><b>Organization:</b> University of Cologne <br/><b>Location:</b> Cologne, Germany <br/> <b>Coordinates:</b> 6.92895, 50.92819 <br/> <b>Description:</b> A test course'; 
	addMarker(lonlat, popupContentHTML, true, true);
cmac2map.addLayer(markers);