Edit in JSFiddle

<div id="map-div" style="width:450px;height:430px;"></div>

map = new OpenLayers.Map({
    div: "map-div",
    projection: new OpenLayers.Projection('EPSG:900913'),
    'displayProjection': new OpenLayers.Projection('EPSG:4326')
});

var osm = new OpenLayers.Layer.OSM();
map.addLayer(osm);

var longitude = -97.0928440;
var latitude = 32.7478770;
var centerlonlat = new OpenLayers.LonLat( longitude , latitude );

centerlonlat=centerlonlat.transform(map.displayProjection, map.projection);
var zoom = 15;
map.setCenter(centerlonlat,zoom);