populate jQuery UI accordion with xml, binding problem

Answer 1

Note the two lines below I added (with comments). You need to destroy and then recreate the accordion.

    $('#valitsija').click(function() {
    $.get('http://www.equstom.fi/kurssit.xml', function(data) {

        //you need to destroy the accordion first
        $('#accordion').accordion("destroy");
        $('#accordion').empty();

        $(data).find('Kurssi').each(function() {

            var $kurssi = $(this);
            var html = '<div>';
            html += '<h3><a href="#">' + $kurssi.find('KurssinNimi').text()  + '</a></h3>';
            html += '<div>' + $kurssi.find('KurssiKuvaus').text() + '</div>';
            html += '</div>';
            $('#accordion').append($(html));

        }); 

        //you need to re-make the accordion
        $("#accordion").accordion({ header: "h3" });
    });
});

I would suggest storing the #accordion into a variable so you don't have to keep searching for it. This is called caching. (I know its not your question, but figured I'd offer this suggestion anyways). Something like this:

$('#valitsija').click(function() {
    $.get('http://www.equstom.fi/kurssit.xml', function(data) {

        var acc = $('#accordion');
        //you need to destroy the accordion first
        acc.accordion("destroy");
        acc.empty();

        $(data).find('Kurssi').each(function() {

            var $kurssi = $(this);
            var html = '<div>';
            html += '<h3><a href="#">' + $kurssi.find('KurssinNimi').text()  + '</a></h3>';
            html += '<div>' + $kurssi.find('KurssiKuvaus').text() + '</div>';
            html += '</div>';
            acc.append($(html));

        }); 

        //you need to re-make the accordion
        acc.accordion({ header: "h3" });
    });
}); 

Proof that it works