se su frames:

function NavJump(list) {
parent.frames[1].location.href = list.options[list.selectedIndex].value;
}


...


<SELECT onChange="NavJump2(this)">
<OPTION selected value="page.htm">Home Page</OPTION>
<OPTION value="services.htm">Servizi</OPTION>
<OPTION value="download.htm">Download</OPTION>
<OPTION value="links.htm">Links</OPTION>
</SELECT>