function content_type_switch(selected)
{
	
	// authors
	if(selected == 1)
	{
		arr_field_status['author'] = 1;
		arr_field_status['subtitle'] = 1;
		arr_field_status['category'] = 0;
	}
	// books (running list)
	elseif(selected == 2)
	{
		arr_field_status['author'] = 1;
		arr_field_status['subtitle'] = 1;
		arr_field_status['category'] = 0;
	}
	// products
	elseif(selected == 3)
	{
		arr_field_status['author'] = 0;
		arr_field_status['subtitle'] = 0;
		arr_field_status['category'] = 1;
	}

	// disable/enable appropriate fields
	for(i in arr_field_status)
	{
		if(arr_field_status[i] == 1)
		{
			document.getElementById(i).value = '';
			document.getElementById(i).disabled = true;
		}
		else
		{
			document.getElementById(i).disabled = false;
		}
	}
}