Someone

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html>
<head>
<title>Test Page</title>
<script type="text/javascript">
function doChange(srcE, targetId)
{
	var val = srcE.options[srcE.selectedIndex].value;
	var targetE = document.getElementById(targetId);
	alert(val);
	removeAll(targetE);
	if(val == 'languages')
	{
		addOption('C++', targetE);
		addOption('Java', targetE);
		addOption('Scheme', targetE);
	}
	else if(val == 'tools')
	{
		addOption('Visual Studio', targetE);
		addOption('Netbeans', targetE);
		addOption('Eclipse', targetE);
	}
}

function addOption(value, e)
{
	var o = new Option(value);
	try
	{
		e.add(o);
	}
	catch(ee)
	{
		e.add(o, null);
	}
}

function removeAll(e)
{
	for(var i = 0, limit = e.options.length; i < limit - 1; ++i)
	{
		e.remove(1);
	}
}
</script>
</head>
<body>
<form action="#">
	<select name="selOne" id="selOne" onchange="doChange(this, 'selTwo')">
		<option value="default">---Select Something---</option>
		<option value="languages">Languages</option>
		<option value="tools">Tools</option>
	</select>
	<select name="selTwo" id="selTwo">
		<option value="default">---Select Something---</option>
	</select>
</form>
</body>
</html>