Try this
Here is the old DEMO:
EDIT:
(Here is a working DEMO with Bootstrap 3 and jQuery 1.8.3)
$(document).ready(function() {
$('#modal-content').modal('show');
$('#modal-content').on('shown', function() {
$("#txtname").focus();
})
});
Starting bootstrap 3 need to use shown.bs.modal event:
$('#modal-content').on('shown.bs.modal', function() {
$("#txtname").focus();
})