Social Networking :: How To Center Map As Per Marker Locations In Google Maps V3

I have wriiten the following code to avoid zoomout of the markers and to place the makers center to the map.

var bounds=new google.maps.LatLngBounds();map.fitBounds(bounds);map.setCenter(bounds.getCenter());

The above code is working correctly.But when i wrote setInterval function to drop the markers after a specific interval of time , the above piece of code is not working and the map is not getting displayed.This the code i have written

window.onload = function () {
var mapOptions = {
center: new google.maps.LatLng(markers[0].lat, markers[0].lng),
mapTypeId: google.maps.MapTypeId.ROADMAP
};
var infoWindow = new google.maps.InfoWindow();

[Code] ....