Maybe the below would help:
<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8"/>
<meta http-equiv="X-UA-Compatible" content="IE=edge">
<meta name="viewport" content="width=device-width, initial-scale=1">
<title>Page Title</title>
<style>
* {
box-sizing: border-box;
}
body {
font-family: Times, "Times New Roman", "serif";
background-color: #FFFFFF;
}
.container {
width: 80%;
max-width: 1024px;
margin: 0 auto;
border: 1px solid #000;
}
.float_left {
float: left;
}
.float_right {
float: right;
}
header h1 {
margin:0;
padding: 30px 0;
font-size: 18px;
color: #92B8DE;
font-weight: 400;
text-align: center;
overflow: hidden;
}
.corporate_logos {
overflow: hidden;
padding: 15px 30px;
}
aside {
float: left;
width: 25%;
background-color: #8999BB;
margin: 0;
padding: 0;
}
.side_menu {
padding: 30px;
}
.side_menu ul {
margin: 0;
padding: 0;
}
.side_menu li {
margin: 0;
padding: 0;
list-style: none;
}
.side_menu a {
text-decoration: none;
color: #fff;
display: block;
padding: 5px 0;
}
.content {
float: left;
width: 75%;
padding: 0 35px;
}
footer {
clear: both;
padding: 10px;
text-align: center;
}
</style>
</head>
<body>
<div class="container">
<header>
<h1>PREVENT LAW FOR CANADIAN PROFESSIONALS</h1>
<div class="corporate_logos">
<img src="images/scales-preventive.gif" alt="Scales of Justice" class="float_left">
<img src="images/preventivelawreporter.gif" alt="Law Reporter" class="float_right">
</div>
<!-- end corporate_logos -->
<nav class="top_menu">
<ul>
<li><a href="#">Elementary & Secondary</a></li>
<li><a href="#">Post-Secondary</a></li>
<li><a href="#">Research Services</a></li>
<li><a href="#">Research Login</a></li>
<li><a href="#">Subscribe </a></li>
<li><a href="#">Renew</a></li>
<li><a href="#">Contact Us</a></li>
</ul>
</nav>
<!-- end top_nav -->
</header>
<!-- end header -->
<div class="main_content_wrapper">
<aside>
<nav class="side_menu">
<ul>
<li><a href="#">Login</a></li>
<li><a href="#">Research Services</a></li>
<li><a href="#">Testimonials</a></li>
<li><a href="#">Links</a></li>
<li><a href="#">Subscribe</a></li>
<li><a href="#">Renew</a></li>
</ul>
</nav>
<!-- end main_menu -->
</aside>
<main class="content">
<h3>MAIN CONTENT should be to the right of the top/bottom sidebars</h3>
</main>
<!-- end content -->
</div>
<!-- end main_content_wrapper -->
<footer>
<h3>Footer - Preventive Law Reporter</h3>
</footer>
<!-- end footer -->
</div>
<!-- end container -->
</body>
</html>