Edit this expression to turn fixed bottom in fixed top

this function is supoused to work in iphone,

$(document).ready(function() {
    $('#head').css('position','fixed');
  window.onscroll = function() {
      document.getElementById('head').style.top =
         (window.pageYOffset + window.innerHeight + 25) + 'px';
        // alert((window.pageYOffset + window.innerHeight - 25) + 'px');
    };
});

but it's supo开发者_开发知识库used to keep the div (25px) at the bottom of the page, i need it on top of the page no matter how much i scroll

i'm tring like this

$(document).ready(function() {
    $('#head').css('position','fixed');
    var height = $('#head').height();
  window.onscroll = function() {
      document.getElementById('head').style.top =
         (window.pageYOffset) - height + 'px';
        // alert(window.pageYOffset); alert(window.innerHeight);
    };
});

but it seems that the #head div is not following properly the scroll (it seems like it bounces), any idea what i'm missing??

Position fixed do not work in iPhone. So it is bound to bounce whenever you scroll the page until the scroll handler set its new position.

$(document).ready(function() {
    $('#head').css('position','absolute');
    $(window).scroll(function() {
      $('#head').css({
         top: window.pageYOffset
      });
    });
});

Try a little more jQuery:

window.onscroll = function() { $('#head').offset(0,0); }