isto e o meu ficheiro logout.php
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1" />
<script type="text/javascript">
var exit=window.confirm("Deseja sair?");
if (exit)
window.location="http://www.abola.pt";
else
window.location="http://www.record.pt";
</script>
<title>Logout</title>
</head>
<body onunload="window.confirm()">
</body>
</html>
este e o menu.html (que e uma das 3 frames da minha pagina_principal.php
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1" />
<link href="estilomenu.css" rel="stylesheet" type="text/css" />
<title>Menu</title>
</head>
<body">
<div id="corpo">
<div id="conteudo">
<ul>
<li>
<div align="left"><a href="#" tabindex="1"><img src="images/paginas.png" width="50" height="50" border="0" align="absmiddle" /> Páginas</a></div>
</li>
<li>
<div align="left"><a href="#" tabindex="2"><img src="images/menus.png" width="50" height="50" border="0" align="absmiddle" /> Menus</a></div>
</li>
<li>
<div align="left"><a href="upload.php" target ="showframe"><img src="images/imagens.png" width="50" height="50" border="0" align="absmiddle" /> Imagens</a></div>
</li>
<li>
<div align="left"><a href="#" tabindex="4"><img src="images/definicoes.png" width="50" height="50" border="0" align="absmiddle" /> Definições</a></div>
</li>
<li>
<div align="left"><a href="#" tabindex="5"><img src="images/site.png" width="50" height="50" border="0" align="absmiddle" /> Ver Website</a></div>
</li>
<li>
<div align="left"><a href="logout.php" target ="_top"><img src="images/logout.png" width="50" height="50" border="0" align="absmiddle" /> Sair</a></div>
</li>
</ul>
</div>
</div>
</body>
</html>