rem: if (px != null) { 
add: if (px == null) { marker.display(false); } else { 
context:     drawMarker: function(marker) {        var px = this.map.getLayerPxFromLonLat(marker.lonlat);        if (px != null) {            var markerImg = marker.draw(px);            if (!marker.drawn) {                this.div.appendChild(markerImg);                marker.drawn = true;            }        }    },
meta: 4411	/local1/tlutelli/issta_data/temp/all_js/javascript/2006_temp/2006/4411/b4a3bfa9c21d9bad6ad6e0ff477f2acb3c72f08d/Markers.js/buggy/lib/OpenLayers/Layer/Markers.js