Edit in JSFiddle

var map;
function initialize()
{
    var myLatlng = new google.maps.LatLng(28.635157,77.22496);
    map = new google.maps.Map(document.getElementById("map"),
    {
        zoom: 14,
        center: myLatlng,
        mapTypeId: google.maps.MapTypeId.ROADMAP
    });

    google.maps.event.addListener(map, 'click', function(event)
    {
        placeMarker(event.latLng);
    });
}

function placeMarker(location)
{
    var marker = new google.maps.Marker(
    {
        position: location,
        map: map
    });

    var coords = location.lat().toFixed(6) + ', ' + location.lng().toFixed(6);

    var infowindow = new google.maps.InfoWindow(
    {
        content: 'The latitude longitude co-ordinates are: ' + coords
    });

    google.maps.event.addListener(marker, 'click', function()
    {
        infowindow.open(map,marker);
    });
}
<html>
<head>
<title>
Adding markers and info windows on click and retrieving the latitude-longitude co-ordinates in the info window
</title>
<script type="text/javascript" src="http://maps.google.com/maps/api/js?sensor=false">
</script>
<script type="text/javascript">
</script>
</head>
<body onload="initialize()">
<div id="map" style="width: 530px; height: 230px">
</div>
 </body>
</html>