Do not load HTML headers after session_start ()

After switching on the session mechanism, the external CSS, JS files, etc. cease to load external files. What could be options?

<?php
     session_start();   
 ?>   
<html>
<head>    
    <meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
    <!--common libs-->
    <link rel="stylesheet" href="../blueprint/screen.css" type="text/css" media="screen, projection">
    <link rel="stylesheet" href="../blueprint/print.css" type="text/css" media="print">
    <!--[if lt IE 8]>
      <link rel="stylesheet" href="css/blueprint/ie.css" type="text/css" media="screen, projection">
    <![endif]-->
    <script type="text/javascript" src="../js/jquery/jquery-1.6.2.min.js"></script>
    <!--custom-->
    <link rel="stylesheet" href="../css/main.css" type="text/css" media="screen, projection">
    <script type="text/javascript" src="../js/main.js"></script>
    <title></title>  
    <script>
        <?php
            if (!isset($_SESSION['page'])){        
                echo 'sendRequest({action:"view"})';
            }
        ?>    
    </script>
</head>
<body>
</body>
</html>

Answer 1, Authority 100%

file is accidentally not utf8 with bom if yes – then the BOM from the file to remove