header.php

<nav class="navbar navbar-expand-lg navbar-light bg-light border-bottom" >
    <div id="logoDiv">
        <a href="./index.php">
            <img src="./images/The Blog Mart.png" alt="The Blog Mart" id="logoImg">
        </a>
    </div>
    <button class="navbar-toggler" type="button" data-toggle="collapse" data-target="#navbarSupportedContent" aria-controls="navbarSupportedContent" aria-expanded="false" aria-label="Toggle navigation">
        <span class="navbar-toggler-icon"></span>
    </button>
    <div class="collapse navbar-collapse" id="navbarSupportedContent">
        <ul class="navbar-nav ml-auto mt-2 mt-lg-0">
            <li class="nav-item"><a class="nav-link" href="./index.php">Home</a></li>
            <li class="nav-item"><a class="nav-link" href="#">About Us</a></li>
            <li class="nav-item"><a class="nav-link" href="#">Contact Us</a></li>
            <li class="nav-item"><a class="nav-link" href="#">Privacy Policy</a></li>
            <li class="nav-item"><a class="nav-link" href="#">Terms &amp; Conditions</a></li>
        </ul>
    </div>
</nav>