通过重写alert方法，重新定义弹窗样式

话不多说上JS

//弹窗更改样式的js
//配合zh-cn.default.css 使用
window.alert = function(str)
{
var shield = document.createElement("DIV"); 
shield.id = "shield"; 
shield.style.height = document.body.scrollHeight+"px";
shield.style.background = "#fff"; 
shield.style.textAlign = "center"; 
shield.style.zIndex = "25";
var alertFram = document.createElement("DIV"); 
alertFram.id="alertFram"; 
alertFram.style.position = "absolute"; 
alertFram.style.left = "50%"; 
alertFram.style.top = "50%"; 
alertFram.style.marginLeft = "-225px"; 
alertFram.style.marginTop = "-75px"; 
alertFram.style.width = "450px"; 
alertFram.style.height = "150px";
alertFram.style.textAlign = "center"; 
alertFram.style.lineHeight = "150px";
alertFram.style.zIndex = "300";
strHtml = "
\n";
strHtml += "
\n";
strHtml += "
\n";
strHtml += "×\n";
strHtml += "
"+str+"
";
strHtml += "
\n";
strHtml += "
\n";
strHtml += "确认\n";
strHtml += "
\n";
strHtml += "
\n";
strHtml += "
\n";
alertFram.innerHTML = strHtml; 
document.body.appendChild(alertFram); 
document.body.appendChild(shield);
this.doOk = function(){ 
alertFram.style.display = "none"; 
shield.style.display = "none"; 
} 
alertFram.focus(); 
document.body.onselectstart = function(){return false;}; 
}