待改进的alert与confirm

<script>
    window.alert=function(info)
    {
        var p = document.createElement("DIV");
        if (!info) var info = '谢谢支持ajax中国http://www.okajax.com';
        p.id = "p";
        p.style.position = "absolute";
        p.style.width = document.body.scrollWidth;
        p.style.height = (document.body.offsetHeight > document.body.scrollHeight) ? '100%' : document.body.scrollHeight;
        p.style.zIndex = '998';
        p.style.top = '0px';
        p.style.left = '0%';
        p.style.backgroundColor = "gray";
        p.style.opacity = '0.5';
        p.style.filter = "alpha(opacity=80)";
        document.body.appendChild(p);
        var p1 = document.createElement("DIV");
        var top = parseInt(parseInt(document.body.scrollHeight) * 0.25) + document.body.scrollTop;
        p1.style.position = "absolute";
        p1.style.width = "300px";
        p1.id = "p1";
        var left = Math.ceil(((document.body.scrollWidth) - parseInt(p1.style.width.replace('px', ''))) / 2) + document.body.scrollLeft;
        p1.style.height = "100px";
        p1.style.zIndex = '999';
        p1.style.top = top + 'px';
        p1.style.left = left + 'px';
        p1.style.border = "0px solid gray";
        var html = "";
        html += "<center>"
        html += "<div class='p3' style='height:1px;overflow:hidden;background:gray;width:294px;border-left:1px solid gray;border-right:1px solid gray;'></div>"
        html += "<div class='p2' style='height:1px;overflow:hidden;background:gray;width:296px;border-left:1px solid gray;border-right:1px solid gray;'></div>"
        html += "<div class='p2' style='height:1px;overflow:hidden;background:gray;width:298px;border-left:1px solid gray;border-right:1px solid gray;'></div>"
        html += "<div class='p1' style='height:20px;overflow:hidden;background:gray;width:300px;border-left:1px solid gray;border-right:1px solid gray;color:#fff;font-size:9pt;font-weight:bold;text-align:left;'> ⊙ 提示</div>"
        html += "<div id='c' style='height:150px;width:300px;background-color:#FEEACB;overflow:hidden;border-left:1px solid gray;border-right:1px solid gray;padding-top:40px;font-size:9pt;'>" + info + "<br><br><br>[ <a href='javascript:this.cancle()'>关闭</a> ]</div>"
        html += "<div class='p1' style='height:1px;overflow:hidden;background:#FEEACB;width:298px;border-left:1px solid gray;border-right:1px solid gray;'></div>"
        html += "<div class='p2' style='height:1px;overflow:hidden;background:#FEEACB;width:296px;border-left:1px solid gray;border-right:1px solid gray;'></div>"
        html += "<div class='p3' style='height:1px;overflow:hidden;background:gray;width:294px;border-left:1px solid gray;border-right:1px solid gray'></div>"
        html += "</center>"
        document.body.appendChild(p1);
        p1.innerHTML = html;
        var arr = document.getElementsByTagName("select");
        var i = 0;
        while (i < arr.length)
        {
            arr[i].style.visibility = 'hidden';
            i++;
        }
        this.cancle = function()
        {
            document.body.removeChild(document.getElementById('p'));
            document.body.removeChild(document.getElementById('p1'));
            var arr = document.getElementsByTagName("select");
            var i = 0;
            while (i < arr.length)
            {
                arr[i].style.visibility = 'visible';
                i++;
            }
        }
    }
</script>
<input value='shout Down' type='button' onclick='alert("您的提交已经完成。")' />