$('span').click(function(){
  var $this = $(this);
  if(!$this.data('changed')){
     $this.data('changed', true);
     $this.html(' ');
  }
}).blur(function(){
  var $this = $(this);
  var trimmedText = $this.text().trim();
  if(trimmedText == "" || trimmedText == "."){
    $this.text('Try me here ');
    $this.data('changed', false);
  }
});