index.html

<!DOCTYPE html>
<html lang="en">
<head>
  <style>
body  {
  background:linear-gradient(rgba(255,255,255,.5), rgba(255,255,255,.5)),url({{ url_for('static', filename='img/healthcare-background.jpg') }})
  
}
</style>
  <title>Heart Disease Detection</title>
  <meta charset="utf-8">
  <meta name="viewport" content="width=device-width, initial-scale=1">
  <link rel="stylesheet" href="https://maxcdn.bootstrapcdn.com/bootstrap/3.4.0/css/bootstrap.min.css">
  <script src="https://ajax.googleapis.com/ajax/libs/jquery/3.4.0/jquery.min.js"></script>
  <script src="https://maxcdn.bootstrapcdn.com/bootstrap/3.4.0/js/bootstrap.min.js"></script>
</head>
<body>

<nav class="navbar navbar-default">
  <div class="container-fluid">
    <div class="navbar-header">
      <a class="navbar-brand" href="/home">Heart Disease</a>
    </div>
    <ul class="nav navbar-nav">
	  <li class="active"><a href="/home">Home</a></li>
      <li><a href="/register">Register</a></li>
	  <li><a href="/prediction">Prediction</a></li>
      
      <li><a href="/about">About Us</a></li>
    </ul>
  </div>
</nav>
</body>
</html>