<script language="javascript">
var regiondb = new Object()
regiondb["africa"] = [{value:"102", text:"Каир"},
                            {value:"88", text:"Лагос"},
                            {value:"80", text:"Найроби"},
                            {value:"55", text:"Претория"}];
				   
regiondb["asia"] = [{value:"30", text:"Анкара"},
                          {value:"21", text:"Бангкок"},
                          {value:"49", text:"Пекин"},
                          {value:"76", text:"Нью-Дели"},
                          {value:"14", text:"Токио"}];
					  
regiondb["australia"] = [{value:"64", text:"Сува"},
                                {value:"12", text:"Сидней"},];
					  
regiondb["europe"] = [{value:"11", text:"Афины"},
                             {value:"35", text:"Франкфурт"},
                             {value:"3", text:"Лондон"},
                             {value:"15", text:"Мадрид"},
                             {value:"1", text:"Париж"},
                             {value:"10", text:"Рим"},
                             {value:"6", text:"Стокгольм"},
                             {value:"97", text:"Санкт-Питербург"}];
					  
regiondb["noamer"] = [{value:"73", text:"Даллас"},
                              {value:"71", text:"Лос-Анджелес"},
                              {value:"5", text:"Нью-Йорк"},
                              {value:"37", text:"Торонто"}];
					  
regiondb["soamer"] = [{value:"65", text:"Буэнос-Айрес"},
                              {value:"31", text:"Каракас"},
                              {value:"66", text:"Рио-де-Жанейро"}];
</script>
<form action="" method="post" target="_self">
	<select name="continent" onchange="setCities(this)" size="10">
		<option value="" selected>Выберите область:</option>
		<option value="africa">Африка</option>
		<option value="asia">Азия</option>
		<option value="australia">Австралия</option>
		<option value="europe">Европа</option>
		<option value="noamer">Северная Америка</option>
		<option value="soamer">Южная Америка</option>
	</select> 
	<select name="city" size="10">
		<option value="" selected>Выберите город:</option>
<script>
function setCities(chooser)
{
	var newElem;
	var where = (navigator.appName =="Microsoft Internet Explorer") ? - 1  : null;
	var cityChooser = chooser.form.elements["city"];
	while (cityChooser.options.length)
	{
		cityChooser.remove( 0 );
	}
	var choice = chooser.options[chooser.selectedIndex].value;
	var db = regiondb[choice];
	newElem = document.createElement("option");
	newElem.text = "Выберите город:";
	newElem.value = "";
	cityChooser.add(newElem, where);
	if (choice != "")
	{
		for (var i= 0 ;i<db.length;i++)
		{
			newElem = document.createElement("option");
			newElem.text = db[i].text;
			newElem.value = db[i].value;
			cityChooser.add(newElem, where);
		}
	}
}
</script>
</form>

var db = regiondb[choice];