$(function() {
    $(".row").each(function() {
        var mid = $(this).children(".mid");
        var left = $(this).children(".left");
        var right = $(this).children(".right");

        if (left.html() != "") {
            var marginLeft = left.css("width");
            mid.css("margin-left", marginLeft);
        }
        else
            left.remove();

        if (right.html() != "") {
            var marginRight = right.css("width");
            mid.css("margin-right", marginRight);
        }
        else
            right.remove();

    });
});