function isIE() {
    if (navigator.userAgent.match(/MSIE \d\.\d+/))
        return true;
    return false;
}

function zIndexWorkaround() {
    if (isIE()) {
        var zi = 1000;
        $$("div.block").each(function(block) {
            block.style.zIndex = zi--;
        });
    }
}