headerBackend.php

<!--Styles are referenced below. Your stylesheets can be more descriptive if need be-->
<link rel="stylesheet" type="text/css" href="css/styles1.css" />
<link rel = "stylesheet" type = "text/css"href="css/styles2.css"/>
<!--This is the  little picture that you see on the tabs in your browser-->
<link rel='shortcut icon' href='images/yourIcon' />

<?php
// You can make a certain style load only on a certain page
if($_GET['page']=="fileName3")
{print"<link rel=\"stylesheet\" type=\"text/css\" href=\"css/styles3.css\" />\n";}
?>

<!--These are some good libraries to look into for web development-->

 <!--Latest Minified Version of boostrap -->
<link rel="stylesheet" href="https://maxcdn.bootstrapcdn.com/bootstrap/3.3.7/css/bootstrap.min.css" integrity="sha384-BVYiiSIFeK1dGmJRAkycuHAHRg32OmUcww7on3RYdg4Va+PmSTsz/K68vbdEjh4u" crossorigin="anonymous" />

<!-- jQuery library -->
<script src="https://ajax.googleapis.com/ajax/libs/jquery/3.2.1/jquery.min.js"></script>

<!-- Latest compiled JavaScript -->
<script src="https://maxcdn.bootstrapcdn.com/bootstrap/3.3.7/js/bootstrap.min.js"></script>

<!--import jqQuery-ui CSS for datepicker-->
<link rel='stylesheet' href='https://code.jquery.com/ui/1.12.1/themes/base/jquery-ui.css' />

<!--import jQuery library from jQuery CDN-->
<script type='text/javascript' src='https://code.jquery.com/jquery-3.1.1.min.js'></script>

<!--import jQuery-ui JS for datepicker-->
<script type='text/javascript' src='https://code.jquery.com/ui/1.12.1/jquery-ui.js'></script>
<script src="https://ajax.googleapis.com/ajax/libs/angularjs/1.6.4/angular.min.js"></script>