$(document).ready(function(){ 
sAlert("公告","内容");
}); 

function sAlert(strTitle,strContent){

 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.title = "点击关闭";
 title.innerHTML="<table border=‘0‘ width=‘100%‘><tr><td align=‘left‘><b>"+ strTitle +"</b></td><td>关闭</td></tr></table></div>";
 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=strContent;
 document.getElementById("msgDiv").appendChild(txt);
}