美化alert

    <input type="button" value="点击这里" onclick="alert2('测试效果');" />

function alert2(str) {
    var msgw,msgh,bordercolor;
    msgw = 400;//提示窗口的宽度
    msgh = 100;//提示窗口的高度
    titleheight = 25 //提示窗口标题高度
    bordercolor = "#336699";//提示窗口的边框颜色
    titlecolor = "#99CCFF";//提示窗口的标题颜色

    var sWidth,sHeight;
    sWidth = document.body.offsetWidth;
    sHeight = screen.height;
    var bgObj = document.createElement("div");
    bgObj.setAttribute('id', 'bgDiv');
    bgObj.style.position = "absolute";
    bgObj.style.top = "0";
    bgObj.style.background = "#777";
    bgObj.style.filter = "progid:DXImageTransform.Microsoft.Alpha(style=3,opacity=25,finishOpacity=75";
    bgObj.style.opacity = "0.6";
    bgObj.style.left = "0";
    bgObj.style.width = sWidth + "px";
    bgObj.style.height = sHeight + "px";
    bgObj.style.zIndex = "10000";
    document.body.appendChild(bgObj);

    var msgObj = document.createElement("div")
    msgObj.setAttribute("id", "msgDiv");
    msgObj.setAttribute("align", "center");
    msgObj.style.background = "white";
    msgObj.style.border = "1px solid " + bordercolor;
    msgObj.style.position = "absolute";
    msgObj.style.left = "50%";
    msgObj.style.top = "50%";
    msgObj.style.font = "12px/1.6em Verdana, Geneva, Arial, Helvetica, sans-serif";
    msgObj.style.marginLeft = "-225px";
    msgObj.style.marginTop = -75 + document.documentElement.scrollTop + "px";
    msgObj.style.width = msgw + "px";
    msgObj.style.height = msgh + "px";
    msgObj.style.textAlign = "center";
    msgObj.style.lineHeight = "25px";
    msgObj.style.zIndex = "10001";

    var title = document.createElement("h4");
    title.setAttribute("id", "msgTitle");
    title.setAttribute("align", "right");
    title.style.margin = "0";
    title.style.padding = "3px";
    title.style.background = bordercolor;
    title.style.filter = "progid:DXImageTransform.Microsoft.Alpha(startX=20, startY=20, finishX=100, finishY=100,style=1,opacity=75,finishOpacity=100);";
    title.style.opacity = "0.75";
    title.style.border = "1px solid " + bordercolor;
    title.style.height = "18px";
    title.style.font = "12px Verdana, Geneva, Arial, Helvetica, sans-serif";
    title.style.color = "white";
    title.style.cursor = "pointer";
    title.innerHTML = "关闭";
    title.onclick = function() {
        document.body.removeChild(bgObj);
        document.getElementById("msgDiv").removeChild(title);
        document.body.removeChild(msgObj);
    }
    document.body.appendChild(msgObj);
    document.getElementById("msgDiv").appendChild(title);
    var txt = document.createElement("p");
    txt.style.margin = "1em 0"
    txt.setAttribute("id", "msgTxt");
    txt.innerHTML = str;
    document.getElementById("msgDiv").appendChild(txt);
}