function save_task(task_id, task_url) {
    console.log('Saving task to', task_url);

    var $form = $('.task form');
    var $button = $form.find("button[type='submit']");
    var payload = $form.serialize();

    $button.attr('disabled', true);

    if (console) console.log('Sending:', payload);
    $.post(task_url, payload)
        .done(function(data) {
            if (console) console.log('Done saving', data);

            // Update the task list.
            // NOTE: this is tightly linked to the HTML of the task list in for_project.jade.
            $('#task-' + task_id).text($form.find("input[name='name']").val());
        })
        .fail(function(xhr_or_response_data) {
            // jQuery sends the response data (if JSON), or an XHR object (if not JSON).
            if (console) console.log('Failed saving', xhr_or_response_data);
            $('#task-details').html(xhr_or_response_data.responseText);
        })
        .always(function() {
            $button.attr('disabled', false);
        })
        ;

    return false; // prevent synchronous POST to current page.
}