Podés evitarte ajax con algo así
Código HTML:
Ver original<!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"> <meta http-equiv="content-type" content="text/html; charset=utf-8" />
/*<![CDATA[*/
html,body{
margin: 0;
padding: 0;
border: none;
height: 100%;
overflow-y: hidden;
}
.barra{
width: 100%;
height:auto;
padding: 5px 0;
margin: 0;
background:#202020;
}
#destino{
width: 100%;
border: none;
margin: 0;
height: 95%;
}
/*]]>*/
<script type="text/javascript"> //<![CDATA[
function cambiar(){
var opcion = document.getElementById('temas').value;
if(opcion != ""){
document.getElementById('destino').src = opcion;
}
}
//]]>
<select id="temas" onchange="cambiar();"> <option value="http://www.w3schools.com/tags/att_iframe_marginheight.asp">W3Schools
</option> <iframe src="about:blank" id="destino" name="destino"></iframe>
Saludos