$()(function(){
 var input = document.createElement("input");
    if(('placeholder' in input)==false) { 
  $('[placeholder]').focus(function() {
   var i = $(this);
   if(i.val() == i.attr('placeholder')) {
    i.val('').removeClass('placeholder');
    if(i.hasClass('password')) {
     i.removeClass('password');
     this.type='password';
    }   
   }
  }).blur(function() {
   var i = $(this); 
   if(i.val() == '' || i.val() == i.attr('placeholder')) {
    if(this.type=='password') {
     i.addClass('password');
     this.type='text';
    }
    i.addClass('placeholder').val(i.attr('placeholder'));
   }
  }).blur().parents('form').submit(function() {
   $(this).find('[placeholder]').each(function() {
    var i = $(this);
    if(i.val() == i.attr('placeholder'))
     i.val('');
   })
  });
 }
});

<input type="text" name="id" placeholder="ID">