Had a look at your code on the link you posted. This should do the trick:
var reachedTarget = false; // Prevent animation collisions with this
var targetScroll = $('#scroll_verder').position().top;
$(window).scroll(function () {
var currentScroll = $('html').scrollTop() || $('body').scrollTop();
if ( currentScroll >= targetScroll ) {
if ( !reachedTarget ) {
$('.navbar').stop();
$('.navbar').addClass('show-menu').animate({ top: '0px' });
}
reachedTarget = true;
} else{
if ( reachedTarget ) {
$('.navbar').stop();
$('.navbar').removeClass('show-menu').animate({ top: '-50px' });
}
reachedTarget = false;
}
});
EDIT: In CSS (to make sure initial position is correct):
.navbar.show-menu {
z-index: 999;
display: block;
top : -50px;
}