$(document).ready(function(){
  
  $("#navi a").click(function(){
    var offset = $($(this).attr("href")).offset().top; // offset of the element to go to (number of pixels from the top)
    $('html, body').animate({
      scrollTop: offset
    }, 2000); // time to get to the element
  		return false; // ignore link, run only javascript  
  });

});