OpenLayers : Map not loading

Question

If i use a single wmslayer as map baselayer it loads the map, but adding different layers like (google,yahoo) to map it won't works. Can anyone tell me how to overcome this.. thanks in advance.. please check this:

    <script src="http://maps.google.com/maps/api/js?sensor=false&v=3.3" type="text/javascript"></script>
    <script src="http://api.maps.yahoo.com/ajaxymap?v=3.0&appid=abcdefg1234" type="text/javascript"></script>
    <script src="http://openlayers.org/api/OpenLayers.js" type="text/javascript"></script>

    <script type="text/javascript">
        var map;

        function init() {
           map = new OpenLayers.Map('map');

           var googleLayer = new OpenLayers.Layer.Google("Google", { 'sphericalMercator': true,
                                'maxExtent': new OpenLayers.Bounds(-20037508.34, -20037508.34, 20037508.34, 20037508.34)});
           var wmsLayer = new OpenLayers.Layer.WMS("OpenLayers WMS", 
                                            "http://vmap0.tiles.osgeo.org/wms/vmap0", { layers: 'basic' });
           var yahooLayer = new OpenLayers.Layer.Yahoo("Yahoo");

           map.addLayers([googleLayer, wmsLayer, yahooLayer]);

           map.setCenter(new OpenLayers.LonLat(75.5, 8.5), 5);
           map.addControl(new OpenLayers.Control.LayerSwitcher());
           map.addControl(new OpenLayers.Control.MousePosition());
        }
    </script>

Answer 1

i think this is the problem of projection or resolution.

try to use OSM instead of "http://vmap0.tiles.osgeo.org/wms/vmap0".

map.addLayer(new OpenLayers.Layer.OSM());

i hope it helps you...