ko.bindingHandlers.fadeVisible = {
    init: function (element, valueAccessor) {
        var value = valueAccessor();
        $(element).toggle(ko.utils.unwrapObservable(value));
    },
    update: function (element, valueAccessor) {
        var value = valueAccessor();
        ko.utils.unwrapObservable(value) ? $(element).fadeIn('fast') : $(element).fadeOut('fast');
    }
};