$(document).ready(function () {
    setLightboxHeight();

    $(window).resize(function () {
        setLightboxHeight();
    });

    function setLightboxHeight() {
        var heightPercent = 75;
        var lightboxHeight = Math.round($(window).height() * (heightPercent/100));
        $("a.lightbox").each(function (i, e) {
            var jq = $(this);
            var href = jq.attr("href");
            href = href.replace(/height=\d+/, "height=" + lightboxHeight);
            jq.attr("href", href);
        });
    }
});