Try this, just added your scripts inside document ready event of jquery.
<script type="text/javascript">
var optionsList = {
nokia: [
"C6-01",
"E7-00"
],
apple: [
"iPhone 3",
"iPhone 3G",
"iPhone 4"
]
};
$(function () {
var selectBrand = $("#brand");
var selectType = $("#type");
selectBrand.change(function () {
var brand = selectBrand.val();
var options = optionsList[brand];
var html;
if (options) {
html = '<option value="">- select -</option>';
$.each(options, function (index, value) {
html += '<option value="' + value + '">' + value + '</option>';
});
} else {
html = '<option value="">Select a brand</option>';
}
selectType.html(html);
}).change();
});
</script>