javascript 创建自己的alert

javascript代码   图片为mid-nei-bg_02.gif 

     function openAlert(str)
         {                     
             str = "常文字的换行(亚洲文字和非亚洲文字)元素拥有默认的white-space:normal,当定义";
             var imgUrl = "images/mid-nei-bg_02.gif";
             var divAlert = document.createElement("div");    
             divAlert.id = "openAlert";       
             divAlert.style.position="absolute";                      
             divAlert.style.width="280px";
             divAlert.style.border="1px #CCCCFF solid";
             divAlert.style.top="200px";
             divAlert.style.left="-140px";
             divAlert.style.marginLeft="50%";
             divAlert.style.zIndex = "1009";
             divAlert.style.backgroundColor = "White";
                         
             divAlert.innerHTML = "<div style=\"font-size:smaller;100%;height:26px;line-height:26px;background:url("+imgUrl+");\">&nbsp;&nbsp;系统提示框</div>";
             divAlert.innerHTML = divAlert.innerHTML + "<div style=\"40px;float:left;background-color:White;\"><img alt='' src='images/alert.png' border='0'/></div>";
             divAlert.innerHTML = divAlert.innerHTML + "<div style=\"font-size:smaller;240px;text-align:left;float:left;margin-bottom:10px;background-color:white;\"><br/>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;"+str+"</div>";            
             divAlert.innerHTML = divAlert.innerHTML + "<div style=\"100%;text-align:center;margin-bottom:5px;background-color:white;\"><input type='button' value='确定' style=\"background:url("+imgUrl+");border:1px #ccccff solid;40px;height:26px;\" onclick=\"alertOk()\"/></div>";
                         
             createShade();
             document.body.appendChild(divAlert);
             return false;
         }

function createShade()
         {
             var zzDiv = document.createElement("div");
             zzDiv.id = "zzDiv";
             zzDiv.style.filter='alpha(opacity=10)';
             zzDiv.style.backgroundColor = "gray";   
             zzDiv.style.position="absolute";        
             zzDiv.style.left="0px";
             zzDiv.style.top = "0px";
             zzDiv.style.width="100%";
             zzDiv.style.height="100%";
             zzDiv.style.zIndex = "1008";
             zzDiv.style.backgroundColor = "#F3F3F3";
             zzDiv.innerHTML = "&nbsp;";
             document.body.appendChild(zzDiv);
         }
         function alertOk()
         {
            removeOpenAlert();
         }
         function removeOpenAlert()
         {
            window.document.body.removeChild(document.getElementById("openAlert"));
            window.document.body.removeChild(document.getElementById("zzDiv"));           
         }