Deirdre: Por "suponido". Ahí va, a ver si podéis sacar algo en claro...
Código del primer intento mediante un DIV y un IFRAME:
Código 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>
<title>DIV + IFRAME test</title>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8" />
<style type="text/css">
<!--
/* COMMON RULES */
* { margin: 0px; padding: 0px; }
html, body { height: 100%; }
table { border: none; border-spacing: 0px; empty-cells: show; }
td { border: none; text-align: left; vertical-align: top; }
/* SPECIFIC RULES TO SOLVE THIS TEST */
div { width: 100%; height: 50px; background-color: #FFCC00; }
iframe { width: 100%; height: 100%; border: none; }
-->
</style>
</head>
<body>
<div>NAVIGATION MENU</div>
<iframe src="http://www.forosdelweb.com/" frameborder="0"></iframe>
</body>
</html>
Código del segundo intento mediante una TABLE y un IFRAME:
Código 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>
<title>TABLE + IFRAME test</title>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8" />
<style type="text/css">
<!--
/* COMMON RULES */
* { margin: 0px; padding: 0px; }
html, body { height: 100%; }
table { border: none; border-spacing: 0px; empty-cells: show; }
td { border: none; text-align: left; vertical-align: top; }
/* SPECIFIC RULES TO SOLVE THIS TEST */
table { width: 100%; height: 100%; }
tr:first-child td { height: 50px; background-color: #FFCC00; }
tr + tr td { height: 100%; }
iframe { width: 100%; height: 100%; border: none; }
-->
</style>
</head>
<body>
<table border="0" cellspacing="0" cellpadding="0">
<tr>
<td>
NAVIGATION MENU
</td>
</tr>
<tr>
<td>
<iframe src="http://www.forosdelweb.com/" frameborder="0"></iframe>
</td>
</tr>
</table>
</body>
</html>