function changeCarModel(markaSelect, modelSelectId) {

	modelSelect = document.getElementById(modelSelectId);

	for(var i=modelSelect.length; --i>=0; ) {
		modelSelect[i]=null;
	};
	markaId = markaSelect.options[markaSelect.selectedIndex].value;
	markaModels = models[markaId];
	if (markaModels==null) {
		modelSelect.disabled = true;
		return;
	}
	modelSelect.disabled = false;
	var i=0;
	for(var id in markaModels) {
		modelSelect[i] = new Option(markaModels[id], id);
		i++;
	}
}