Trying to add some html and CSS to Custom Block

I have OJS, and I´m trying to upload this code to the Custom Block:

.flex-container {
display: flex;
background-color: #fff;

.flex-container > span {
margin: 4px;
font-size: 50px;
color: #95a5a6;

a, a:hover, a:focus, a:active {
text-decoration: none;
color: inherit;

    <a href="" target="_blank"><i class="fab fa-facebook-square"></i></a>

    <a href="" target="_blank"><i class="fab fa-instagram-square"></i></a>

    <a href="" target="_blank"><i class="fas fa-envelope-square"></i></a>

But it does not work, when a reopen the code custom block window the code is incomplete.
Is there some restriction?
I will appreciate your help

Rennzo Rojas
Kaypunku Lab

Hi @rennzorojas,

You may wish to see the suggestions in this post here:

It might be more better to use the existing CSS structure for the custom block.

Best regards,