Posto le varie pagine... nella timer.htm c'è un bottone che cliccandoci su attiva la stessa funzione location.href del file url_timer.htm e funge..

La funzione 'trova_url' sempre nel timer.htm invece non ne vuole sapere di funzionare

Index.htm
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Frameset//EN" "http://www.w3.org/TR/html4/frameset.dtd">
<html>
<head>
<title>Index</title>
<meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1">
</head>

<frameset rows="30,*" cols="*" framespacing="0" frameborder="NO" border="0">
<frame src="timer.htm" name="timer" scrolling="NO" noresize id="timer" >
<frame src="url.htm" name="url">
</frameset>
<noframes><body>

</body></noframes>
</html>

timer.htm
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
<head>
<title>Documento senza titolo</title>
<meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1">
<script language="javascript">
function trova_url(){
var indirizzo=parent.url.url_timer.location.href;
alert(indirizzo);
}
</script>
</head>

<body leftmargin="0" topmargin="0" marginwidth="0" marginheight="0" onload="javascript:trova_url()";>
<form>
<input type="button" value="No Frames" onClick="top.location.href = parent.url.url_timer.location.href">
</form>

</body>
</html>

url.htm
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Frameset//EN" "http://www.w3.org/TR/html4/frameset.dtd">
<html>
<head>
<title>Documento senza titolo</title>
<meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1">
</head>
<frameset rows="80,*" frameborder="NO" border="0" framespacing="0">
<frame src="url_timer.htm" name="url_timer" scrolling="NO" noresize >
<frame src="url_page.htm" name="url_page">
</frameset>
<noframes><body>
</body></noframes>
</html>

url_timer.htm
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
<head>
<title>Documento senza titolo</title>
<meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1">
</head>

<body>
url_timer
</body>
</html>

url_page.htm
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
<head>
<title>Documento senza titolo</title>
<meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1">
</head>

<body>
url_page
</body>
</html>