Денис Инешин

.my_moudule_namespace--class_name {
    ...
}

/**
 * Remove inner padding and border in Firefox 4+.
 */

button::-moz-focus-inner,
input::-moz-focus-inner {
  border: 0;
  padding: 0;
}

<div class="paravozik">
    Choo-choo
</div>

.paravozik {
    position: fixed;
    bottom: 0; left: 0;
    width: 100px;
    height: 50px;
    background: #000;
}

var $win = $(window),
    $paravozik = $(".paravozik"),
    top = 0,
    height = $(document.body).innerHeight(),
    vpHeight = 0,
    percent = 0;
    
$win.on("scroll", function () {
    top = $win.scrollTop();
    vpHeight = $win.innerHeight();
    percent = top / (height - vpHeight) * 100;
    $paravozik[0].style.left = percent + "%";
});