SweetAlert automatically centers itself on the page and looks great no matter if you're using a desktop computer, mobile or tablet. It's even highly customizeable, as you can see below! http://t4t5.github.io/sweetalert/
A basic sweetalert message
A success message!
A warning message, with a function attached to the "Confirm"-button...
... and by passing a parameter, you can execute something else for "Cancel".
You can easy add sweet alert in your script by adding code (example from warning button):
$('.demo3').click(function () {
swal({
title: "Are you sure?",
text: "You will not be able to recover this imaginary file!",
type: "warning",
showCancelButton: true,
confirmButtonColor: "#DD6B55",
confirmButtonText: "Yes, delete it!",
closeOnConfirm: false
}, function () {
swal("Deleted!", "Your imaginary file has been deleted.", "success");
});
});