This is a note for myself but it could be useful for anybody writing some Ajax calls.
If you use a GET method to send an asynchronous request to your server side code, if you don't do anything Internet Explorer will cache locally your request, so obviously you won't have the latest result in your response.
var url = 'GetCustomers.aspx?country=ireland'
var url = 'GetCustomers.aspx?country=ireland' + "&dummy=" + new Date().getTime();
This will force IE to show a fresh version of your request all the time. Firefox doesn't seem to have this problem apparently.