怎么设置iframe的弹出层在最上面

怎么设置iframe的弹出层在最上面

function setDivCenter(id) {
showDiv(id, "1");
getO(id).style.left = (((parseInt(getWinSize()[0])) - parseInt(getO(id).offsetWidth)) / 2) + "px";
getO(id).style.top = (((parseInt(getWinSize()[1])) - parseInt(getO(id).offsetHeight)) / 2) + "px";
}


function getO(id) {
return document.getElementById(id);
}


function showDiv(id, type) {
if (getO(id) != null) {
var status = ("1" == type) ? "block" : "none";
getO(id).style.display = status;
}
}


function getWinSize() {
var width = parseInt(document.documentElement.clientWidth);
var height = parseInt(document.documentElement.clientHeight);
return new Array(width, height);
}