function getScrollY() {

    scrOfY = 0;

    if( typeof( window.pageYOffset ) == "number" ) {

        scrOfY = window.pageYOffset;

    } else if( document.body && ( document.body.scrollLeft || document.body.scrollTop ) ) {

        scrOfY = document.body.scrollTop;

    } else if( document.documentElement && ( document.documentElement.scrollLeft || document.documentElement.scrollTop ) ) {

        scrOfY = document.documentElement.scrollTop;

    }

    return scrOfY;

}



jQuery(function($){

    var upprev_closed = false;

    var upprev_hidden = true;

    $(window).scroll(function() {

        var lastScreen = getScrollY() + $(window).height() < $(document).height() * 0.7 ? false : true;

        if (lastScreen && !upprev_closed) {

            $("#upprev_box").stop().animate({right:"0px"});

            upprev_hidden = false;

        }

        else if (upprev_closed && getScrollY() == 0) {

            upprev_closed = false;

        }

        else if (!upprev_hidden) {

            upprev_hidden = true;

            $("#upprev_box").stop().animate({right:"-400px"});

        }

    });

    $("#upprev_close").click(function() {

        $("#upprev_box").stop().animate({right:"-400px"});

        upprev_closed = true;

        upprev_hidden = true;

    });

});