JSFiddle - React, Tailwind, and code Playground

HTML

<link rel="stylesheet" href="https://maxcdn.bootstrapcdn.com/font-awesome/4.6.1/css/font-awesome.min.css">
<div class="content">
  <div class="content__row">
    <div class="content__column_half left">
      <span>Join us through VK</span>
    </div>
    <div class="content__column_half right">
      <a href="https://vk.com" class="auth_button">
        <span class="fa fa-vk auth_button__icon"></span>
        <span class="auth_button__text">Sign in</span>
      </a>
    </div>
  </div>
</div>

CSS

/* reset browser styles */
html, body, div, span, object, iframe, h1, h2, h3, h4, h5, h6, p, blockquote, pre, a, abbr, acronym, address, big, cite, code, del, dfn, em, img, ins, kbd, q, s, samp,small, strike, strong, sub, sup, tt, var, b, u, i, center, dl, dt, dd, ol, ul, li, fieldset, form, label, legend,
table, caption, tbody, tfoot, thead, tr, th, td, article, aside, canvas, details, embed,
figure, figcaption, footer, header, hgroup, menu, nav, output, ruby, section, summary,
time, mark, audio, video {
    margin: 0;
    padding: 0;
    border: 0;
    font-size: 100%;
    vertical-align: baseline;
}
article, aside, details, figcaption, figure, footer, header, hgroup, menu, nav, section {
    display: block;
}
body {
    line-height: 1.2;
}
ol {
    padding-left: 1.4em;
    list-style: decimal;
}
ul {
    padding-left: 1.4em;
    list-style: square;
}
table {
    border-collapse: collapse;
    border-spacing: 0;
}
/* end reset browser styles */

body {
    width: 80%;
    margin-left: auto;
    margin-right: auto;
}

.content {
    font-size: 22px;
}

.content__row {
    display: flex;
    height: 250px;
}

.content__column_half {
    flex-grow: 1;
    margin: 0 .5%;
    width: 49%;
    height: 100%;
    box-sizing: border-box;
    padding-top: 30px;
    padding-bottom: 30px;
    border-bottom: 1px dotted #000000;
    background-color: graytext;
}

.content__column_half.left {
    
    padding-right: 30px;
    text-align: right;
}

.content__column_half.right {
    padding-left: 30px;
    text-align: left;
}

.auth_button {
    display: inline-block;
    text-decoration: none;
    color: #ffffff;
    background-color: #4c75a3;
    width: 50%;
    padding-top: 5px;
    padding-bottom: 5px;
    border-radius: 5px;
}

.auth_button:hover {
    background-color: #3a3e97;
}

.auth_button__icon {
    width: 15%;
    text-align: center;
    border-right: 1px solid #ffffff;
}

.auth_button__text {
    padding-left: 5px;
}