From 2014.igem.org
var map, layer;
function init(){
OpenLayers.ProxyHost="/proxy/?url=";
map = new OpenLayers.Map('map');
layer = new OpenLayers.Layer.WMS( "OpenLayers WMS",
"http://vmap0.tiles.osgeo.org/wms/vmap0", {layers: 'basic'} );
map.addLayer(layer);
map.setCenter(new OpenLayers.LonLat(0, 0), 0);
var markers = new OpenLayers.Layer.Markers( "Markers" );
map.addLayer(markers);
var size = new OpenLayers.Size(21,25);
var offset = new OpenLayers.Pixel(-(size.w/2), -size.h);
var icon = new OpenLayers.Icon('http://www.openlayers.org/dev/img/marker.png',size,offset);
markers.addMarker(new OpenLayers.Marker(new OpenLayers.LonLat(0,0),icon));
var halfIcon = icon.clone();
markers.addMarker(new OpenLayers.Marker(new OpenLayers.LonLat(0,45),halfIcon));
marker = new OpenLayers.Marker(new OpenLayers.LonLat(90,10),icon.clone());
marker.setOpacity(0.2);
marker.events.register('mousedown', marker, function(evt) { alert(this.icon.url); OpenLayers.Event.stop(evt); });
markers.addMarker(marker);
map.addControl(new OpenLayers.Control.LayerSwitcher());
map.zoomToMaxExtent();
halfIcon.setOpacity(0.5);
}