/* Constrain header to body width */
    #header {
      -webkit-font-smoothing: antialiased;
      -moz-osx-font-smoothing: grayscale;
      max-width: 1024px;
      margin-left: auto;
      margin-right: auto;}

/* Top-Nav container */
    div.topNav {
      height:2rem;
      max-width:1024px;
      margin:2rem auto;
      text-align:right;}

        /* Telephone Number */
        div.topNav a#topNavPhone {
          display:block;
          float:left;
          padding-top:0.75rem;
          margin-left:2rem;
          color:#57C7C1;}
        div.topNav a#topNavPhone i.fas {margin-right:0.75rem;}

        /* Search Box */
        div.topNav form.catalogSearch {
          display:inline-block;
          width:50%;
          margin-right:0.5rem;}
        div.topNav form.catalogSearch input {
          padding: 0.75em 1em;
          border:1px solid #dbdbdb;
          width:60%;}
        div.topNav form.catalogSearch button {
          position:relative;
          padding: 0.75em 1em;
          left:-8px;
          border:1px solid #dbdbdb;
          background-color:#fafafa;
          color:#ccc;}
        div.topNav form.catalogSearch button:hover {color:#396;}

        /* Login Button */
        div.topNav a#btnLogin {
            display:inline-block;
            background-color: #57C7C1;
            color: white;
            font-weight:600;
            letter-spacing:2px;
            padding: 0.75em 1em;
            border-radius:3px;
            text-decoration: none;
            text-transform: uppercase;
            margin-left:2rem;
            margin-right:2rem;}
        div.topNav a#btnLogin:hover {background-color:#999;}
  
    /* Hide in mobile */
    @media screen and (max-width:640px) {
      div.topNav {
        display: none;
      }
    }

/* Footer column headings */
    div#preFooter div.pre-footer-inner h3 {
      color:#344;
      text-transform:uppercase;
      font-size:1.1rem;}

/* Footer links */
    div#preFooter div.pre-footer-inner p {
      margin-top:0 !important;
      margin-bottom:0 !important;}
    div#preFooter div.pre-footer-inner a {
      color:#4D595C;
      border:none;
      margin-left:0rem;
      font-size:1rem;}
    div#preFooter div.pre-footer-inner a:hover {
      color:#A8847D;
      border-bottom:1px solid #4D595C !important;
      padding-bottom:0.1rem;}

/* *** IN-PROCESS *** Blockquote styles 
for use in landing page intro paragraphs */
blockquote {
    font-family: 'proxima-nova', sans-serif;
    font-size:1.4rem;
    font-weight:300;
    color:#555555;
    line-height:1.75rem;
    letter-spacing:0.25px;
    font-style:normal;
    padding:0;}

/* Back-to-Top btn */
    a.btt {
      display: none;
      position: fixed;
      z-index: 999;
      width: 50px;
      height: 50px;
      right: 30px;
      bottom: 30px;
      background: #ebebeb;
      -webkit-border-radius: 30px;
      -moz-border-radius: 30px;
      border-radius: 30px;
      box-shadow: 3px 3px 10px rgba(23, 25, 25, 0.2);
      transition: transform 0.3s ease-in-out;}
    a.btt .svg-inline--fa {
      color: #191717;
      position: relative;
      height: 100%;
      top: 0;
      left: 50%;
      transform: translateX(-50%);} 
    a.btt:hover{transform: translatey(-4%);}

https://ajax.googleapis.com/ajax/libs/jquery/3.2.1/jquery.min.js

var scrolled = 400;
    $(window).scroll(function() {
        if ( $(window).scrollTop() > scrolled ) {
          $('a.btt').fadeIn('slow');
        } else {
          $('a.btt').fadeOut('slow');
        }
    });
    $('a.btt').click(function() {
      $('html, body').animate({ scrollTop: 0 }, 700);
      return false;
    });