I have a one page site with fixed navigation and using a scroll script, very similar to this: http://www.ivanjevremovic.in.rs/live/temptation/single/orange/index-cycle-slide
Here are all the variables you'll need...
var $myElt = $('.myElement'); // whatever element you want to check
var $window = $(window); // the window jQuery element
var myTop = $myElt.offset().top; // the top (y) location of your element
var windowTop = $window.scrollTop(); // the top of the window
var windowBottom = windowTop + $window.height(); // the bottom of the window
Then to make sure your element is within the window's range...
if (myTop > windowTop && myTop < windowBottom) {
// element is in the window
} else {
// element is NOT in the window
// maybe use this to scroll...
// $('html, body').animate({scrollTop: myTop}, 300);
}
jQuery reference: