HTML source as requested

  <div id="header-content">
    <div id="nav-left">
      <div class="nav-btn-l">Home</div>
      <div class="nav-btn-l">Something</div>
      <div class="nav-btn-l">Something else</div>
    </div>
    <div id="nav-right">
      <div class="nav-btn-r login-button" onclick="floatdiv_load()">Login</div>
      <div class="nav-btn-r" style="margin-right: -12px;">Sign up</div>
    </div>
    <div id="placeholder_one">
    </div>
  </div>