NavBar Bootstrap v4 Fix
<nav class="navbar navbar-expand-sm navbar-dark fixed-top bg-dark">
<div class="container">
<button class="navbar-toggler" type="button" data-toggle="collapse" data-target="#navbarSupportedContent" aria-controls="navbarSupportedContent" aria-expanded="false" aria-label="Toggle navigation">
</button>
<a class="navbar-brand" href="/">Application name</a>
<div class="navbar-collapse collapse" id="navbarSupportedContent">
<ul class="nav navbar-nav mr-auto">
<li class="nav-item"><a href="/" class="nav-link">Home</a></li>
<li class="nav-item"><a href="/Home/About" class="nav-link">About</a></li>
<li class="nav-item"><a href="/Home/Contact" class="nav-link">Contact</a></li>
</ul>
<ul class="nav navbar-nav navbar-right mr-auto">
<li class="nav-item"><a href="/Account/Register" id="registerLink" class="nav-link">Register</a></li>
<li class="nav-item"><a href="/Account/Login" id="loginLink" class="nav-link">Log in</a></li>
</ul>
</div>
</div>
</nav>