JSFiddle - React, Tailwind, and code Playground

HTML

<div id="header-nav">
<ul>
          <li><a href="http://dev.tilbudibyen.com/">DAGENS TILBUD</a></li>
      <li><a href="/alldeals">TIDLIGERE TILBUD</a></li>

                <li><a class="signup" href="#signup-form" id="signup">TILMED DIG</a></li>
      
      
      <li><a href="http://dev.tilbudibyen.com/ipages?p=about" id="iabout" class="ipages">OM OS</a></li>
      <li><a href="http://dev.tilbudibyen.com/ipages?p=contact" id="icontact" class="ipages">KONTAKT OS</a></li>      
      <li><a href="http://dev.tilbudibyen.com/ipages?p=faq" id="ifaq" class="ipages">HJÆLP</a></li>
                <li><a href="#loginform" id="tip5">LOG IND</a></li>
      </ul>
</div>

CSS

*+ html ul {display: block}
*+ html li {display: inline; float:left; height: 100%}

ul {
    display: table;
}
ul, ol{
    list-style: none outside;
}
#header-nav ul { display: table; }
#header-nav ul li {
  display: table-cell;
    width: 140px;
  text-align: center;
  letter-spacing: -0.10em;
  border-left: 1px solid #131313;
  border-right: 1px solid #323232;
  border-bottom: none;
  border-top: none;
}
#header-nav ul li:first-child { border-left: none; }
#header-nav ul li:last-child { border-right: none; vertical-align: middle; }
#header-nav ul li a { 
    color: #000; 
  display: block;
  padding: 10px 0px;
}
#header-nav img { margin: 0px; padding: 0px; }