Código :
<form name="doublecombo">
<p><select name="example" size="1" onChange="redirect(this.options.selectedIndex)">
<option>Tecnología</option>
<option>Noticias</option>
<option>Buscadores</option>
</select>
<select name="stage2" size="1">
<option value="web1">Website Abstraction</option>
<option value="web2">web2_2"</option>
<option value="web3">web3_3</option>
</select>
<input type="button" name="test" value="visitar"
onClick="go()">
</p>
<script>
<!--
var groups=document.doublecombo.example.options.length
var group=new Array(groups)
for (i=0; i<groups; i++)
group[i]=new Array()
group[0][0]=new Option("Web1_1","web1")
group[0][1]=new Option("web2","web2_2")
group[0][2]=new Option("web3_3","web3")
group[1][0]=new Option("CNN","cnn2")
group[1][1]=new Option("ABC","abc2")
group[2][0]=new Option("otra pag","otra_pag2")
group[2][1]=new Option("info","info2")
group[2][2]=new Option("Exci","exci2")
group[2][3]=new Option("Lyc","lyc2")
var temp=document.doublecombo.stage2
function redirect(x){
for (m=temp.options.length-1;m>0;m--)
temp.options[m]=null
for (i=0;i<group[x].length;i++){
temp.options[i]=new Option(group[x][i].text,group[x][i].value)
}
temp.options[0].selected=true
}
function go(){
location=temp.options[temp.selectedIndex].value
}
//-->
</script>
</form>
Tambien aprobechando este mensage me inicio en este foro en el que intentaré ayudar en todo lo posible
