codice:
<form id="form" method="post" action="send_news.php">
                <table>
                    <tr><td>Oggetto: </td><td><input type="text" name="oggetto" id="oggetto" size="100"/></td></tr>
                    <tr><td>Testo: </td><td><textarea value="" cols="100" rows="20" name="testo" id="testo"></textarea></td></tr>
                    <tr><td><input type="reset" value="Cancella" /></td><td><input type="button" value="invia" onclick="ask_()"/></td></tr>

                </table>
            </form>
            <script language="javascript">
                function ask_ (){
                        
                    if(!confirm("Sei sicuro di voler inviare le newsletter?")){
                       location.href = "administration.php";
                       
                    }
					else
					{
						document.getElementById('form').submit();
					};
                        
                }
                
            </script>
impara a mettere gli script js tra i tag head