var div = 1;

    var sliderEnabled = true;
    function scrFol()
    {
        var ad = document.getElementById( 'slider' );
        var dPos = ( document.all ) ? document.body.scrollTop : window.pageYOffset;

        if ( ( dPos == 0 ) && ( document.all ) )
            dPos = document.documentElement.scrollTop;

        dPos += 50;
        var cPos = parseInt( ad.style.top );
        if ( cPos == 0 )
            cPos = dPos-1000;

        var posDif = dPos-cPos;

        if ( ( ad.style.display == 'none' ) && ( sliderEnabled ) )
            ad.style.display = 'block';

        if ( posDif > 0 )
            ad.style.top = (cPos+Math.ceil(posDif/div))+'px';
        else if ( posDif < 0 )
            ad.style.top = (cPos+Math.floor(posDif/div))+'px';

        if ( sliderEnabled )
            setTimeout( 'scrFol()', 20 );
    }
    function closeFollowSlider()
    {
        sliderEnabled = false;
        document.getElementById( 'slider' ).style.display = 'none';
    }

    <!-- A popup lecsúszásának késleltetése -->
    setTimeout( 'scrFol()', 2000 );