I would like to have only 3 levels of zoom available (from level 6 to level 8).
demolayer2 = new OpenLayers.Layer.WMS(
"abc...","http://localhost:8080/geoserver/gwc/service/wms",
{layers: 'def...', transparent:"true", format: 'image/png', numZoomLevels: 3, minZoomLevel: 6 },{isBaseLayer:false},
{ tileSize: new OpenLayers.Size(256,256)});
map.addLayer(demolayer2);
map.addControl(new OpenLayers.Control.LayerSwitcher({'div':OpenLayers.Util.getElement('layerswitcher')}));
map.zoomToExtent(new OpenLayers.Bounds(-4.601615515076983,39.8769407866263,-3.0527184873294764,41.16710732525929));