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;
}

var $j = jQuery.noConflict();

$j(function(){
    $j("body").prepend("<div id='bcp_box'><h6>Mi titulo</h6><a href='http://www.google.com'>Google</a><button id='bcp_close' type='button'>Close</button></div>");
    var bcp_closed = false;
    var bcp_hidden = true;
    $j(window).scroll(function() {
        var lastScreen = getScrollY() + $j(window).height() < $j(document).height() * 0.4 ? false : true;
        if (lastScreen && !bcp_closed) {
            $j("#bcp_box").stop().animate({right:"0px"});
            bcp_hidden = false;
        }
        else if (bcp_closed && getScrollY() == 0) {
            bcp_closed = false;
        }
        else if (!bcp_hidden) {
            bcp_hidden = true;
            $j("#bcp_box").stop().animate({right:"-400px"});
        }
    });
    $j("#bcp_close").click(function() {
        $j("#bcp_box").stop().animate({right:"-400px"});
        bcp_closed = true;
        bcp_hidden = true;
    });
});