$(document).ready(function(){
  if ($('#under13').length) {
    tb_show('', '#TB_inline?height=90&width=450&inlineId=under13', false);
  }
  
  $("#register_username").typeWatch( typeWatchOptions, $("#register_username") );
  
});

var typeWatchOptions = {
    callback:function(){ 
      isNameAvailable(
        $('#register_username'),
        $('#username_notification')
      ); 
    },
    wait:500 // milliseconds
}