XF 1.4 Where can I include this HTML/CSS code?

[Betclever]

Hello all,

I made a page where I put this HTML code:

<div class="row">
  <div class="large-4 medium-4 columns">
     <ul class="pricing-table active-tb shadow mrgn-20-top">
       <li class="title">Starter</li>
       <li class="bullet-item">512 MB RAM</li>
       <li class="bullet-item">50GB Disk</li>
       <li class="bullet-item">1 User</li>
       <li class="bullet-item">4TB bandwidth</li>
       <li class="price">$9</li>
       <li class="cta-button"><a class="button text-transform" href="#">Choose</a></li>
     </ul>
   </div>
  <div class="large-4 medium-4 columns">
     <ul class="pricing-table active-tb shadow mrgn-20-top">
       <li class="title">Starter</li>
       <li class="bullet-item">512 MB RAM</li>
       <li class="bullet-item">50GB Disk</li>
       <li class="bullet-item">1 User</li>
       <li class="bullet-item">4TB bandwidth</li>
       <li class="price">$9</li>
       <li class="cta-button"><a class="button text-transform" href="#">Choose</a></li>
     </ul>
   </div>
  <div class="large-4 medium-4 columns">
     <ul class="pricing-table active-tb shadow mrgn-20-top">
       <li class="title">Starter</li>
       <li class="bullet-item">512 MB RAM</li>
       <li class="bullet-item">50GB Disk</li>
       <li class="bullet-item">1 User</li>
       <li class="bullet-item">4TB bandwidth</li>
       <li class="price">$9</li>
       <li class="cta-button"><a class="button text-transform" href="#">Choose</a></li>
     </ul>
   </div>
</div>

However, when I put this code into the CSS sheet "extra.css", it doesn't work...

      body {
  margin: 2rem; }

.active-tb {
  position: relative;
  box-shadow: 0px 2px 10px 0px rgba(50, 50, 50, 0.5);
  transform: scale(1);
  border: 0;
  transition: 0.4s ease;
  z-index: 13; }
  .active-tb:hover {
    position: relative;
    box-shadow: 0px 2px 10px 0px rgba(50, 50, 50, 0.5);
    transform: scale(1.25);
    border: 0;
    z-index: 15; }

What's wrong please?

Thanks for your help.