.fourty {

    filter:alpha(opacity=40);
}
.fifty {

    filter:alpha(opacity=50);
}
.sixty {

    filter:alpha(opacity=60);
}

var $elements = $('.yourClass');

var $elements = $('*').filter(function() {
    return $(this).css('filter') != 'auto';
});

var $elements = $('*').filter(function() {
    var $element = $(this);
    return $element.css('filter') != 'auto' || $element.css('opacity') != 1;
});

var foundels = [];

$(els).each(function(){
    if($(this).css('filter') == 'alpha(opacity=60)')
        foundels.push(this);
});