ah ok.
allora ti posto come la riceve il browser.

codice:
<html>
<head>
</head>
<body>
        <script language="Javascript">
var IdxsC = new Array();
var OptsN = new Array();

var oOpt;


{
    IdxsC[0] = 1;
    OptsN[0] = new Array();


    {
        oOpt = document.createElement("option");
        oOpt.value =1;
        oOpt.text = Camerun;
        OptsN[$idxC][$idxN] = oOpt;
    }


    {
        oOpt = document.createElement("option");
        oOpt.value =2;
        oOpt.text = Egypt;
        OptsN[$idxC][$idxN] = oOpt;
    }


    {
        oOpt = document.createElement("option");
        oOpt.value =3;
        oOpt.text = Rwanda;
        OptsN[$idxC][$idxN] = oOpt;
    }


    {
        oOpt = document.createElement("option");
        oOpt.value =4;
        oOpt.text = Senegal;
        OptsN[$idxC][$idxN] = oOpt;
    }


    {
        oOpt = document.createElement("option");
        oOpt.value =5;
        oOpt.text = South Africa;
        OptsN[$idxC][$idxN] = oOpt;
    }


    {
        oOpt = document.createElement("option");
        oOpt.value =6;
        oOpt.text = Zambia;
        OptsN[$idxC][$idxN] = oOpt;
    }


}


{
    IdxsC[1] = 2;
    OptsN[1] = new Array();


    {
        oOpt = document.createElement("option");
        oOpt.value =7;
        oOpt.text = Argentina;
        OptsN[$idxC][$idxN] = oOpt;
    }


    {
        oOpt = document.createElement("option");
        oOpt.value =8;
        oOpt.text = Brasil;
        OptsN[$idxC][$idxN] = oOpt;
    }


    {
        oOpt = document.createElement("option");
        oOpt.value =9;
        oOpt.text = Chile;
        OptsN[$idxC][$idxN] = oOpt;
    }


    {
        oOpt = document.createElement("option");
        oOpt.value =10;
        oOpt.text = Colombia;
        OptsN[$idxC][$idxN] = oOpt;
    }


    {
        oOpt = document.createElement("option");
        oOpt.value =11;
        oOpt.text = Cuba;
        OptsN[$idxC][$idxN] = oOpt;
    }


}


{
    IdxsC[2] = 3;
    OptsN[2] = new Array();


    {
        oOpt = document.createElement("option");
        oOpt.value =12;
        oOpt.text = Hong Kong;
        OptsN[$idxC][$idxN] = oOpt;
    }


    {
        oOpt = document.createElement("option");
        oOpt.value =13;
        oOpt.text = India;
        OptsN[$idxC][$idxN] = oOpt;
    }


    {
        oOpt = document.createElement("option");
        oOpt.value =14;
        oOpt.text = Japan;
        OptsN[$idxC][$idxN] = oOpt;
    }


}


{
    IdxsC[3] = 4;
    OptsN[3] = new Array();


    {
        oOpt = document.createElement("option");
        oOpt.value =15;
        oOpt.text = Belgique;
        OptsN[$idxC][$idxN] = oOpt;
    }


    {
        oOpt = document.createElement("option");
        oOpt.value =16;
        oOpt.text = France;
        OptsN[$idxC][$idxN] = oOpt;
    }


    {
        oOpt = document.createElement("option");
        oOpt.value =17;
        oOpt.text = Italia;
        OptsN[$idxC][$idxN] = oOpt;
    }


    {
        oOpt = document.createElement("option");
        oOpt.value =18;
        oOpt.text = Portugal;
        OptsN[$idxC][$idxN] = oOpt;
    }


    {
        oOpt = document.createElement("option");
        oOpt.value =19;
        oOpt.text = Espana;
        OptsN[$idxC][$idxN] = oOpt;
    }


}


function GetOptions(idxC) {
    for(var idx=0; idx<IdxsC.length; idx++) {
        if(IdxsC[idx] == idxC) {
            return OptsN[idx];
        }
    }
    return new Array();
}

function nazione(selezionata) {
    var Opts = GetOptions(selezionata);

    document.form1.seconda.options.length = 0;

    var oOpt = document.createElement("option");
    oOpt.value = "";
    oOpt.text = "";
    document.form1.seconda.options[0] = oOpt;

    for(i=0; i<Opts.length; i++) {
        document.form1.seconda.options[i+1] = Opts[i];
    }
}

        </script>


<form name="form1">
<select name="prima" onChange="nazione(this[this.selectedIndex].value)">
<option value=""></option><option value="1">Africa</option>
<option value="2">Latin America</option>
<option value="3">Asia</option>

<option value="4">Europe</option>
</select>

<select name="seconda"> </select>

</form>

</body>
</html>
come dicevo la combo continenti è popolata, ma in quella delle nazioni non appare nulla.