电网关系知乎:下面代码什么作用?

<!--
var StarTime_S,EndTime_S
var now1 =new Date()
StarTime_S =now1.getTime()
function MM_openBrWindow(theURL,winName,features) {
window.open(theURL,winName,features);}
//-->

//***********默认设置定义.*********************
tPopWait=5;//停留tWait豪秒后显示提示。
tPopShow=5000;//显示tShow豪秒后关闭提示
showPopStep=20;
popOpacity=99;

//***************内部变量定义*****************
sPop=null;
curShow=null;
tFadeOut=null;
tFadeIn=null;
tFadeWaiting=null;

document.write("<style type='text/css'id='defaultPopStyle'>");
document.write(".cPopText { background-color: #ffffff;color:#800000; border: 1px #FCFC38 solid;font-color: font-size: 12px; padding-right: 4px; padding-left: 4px; height: 20px; padding-top: 2px; padding-bottom: 2px; filter: Alpha(Opacity=0)}");
document.write("</style>");
document.write("<div id='dypopLayer' style='position:absolute;z-index:1000;' class='cPopText'></div>");

function showPopupText(){
var o=event.srcElement;
MouseX=event.x;
MouseY=event.y;
if(o.alt!=null && o.alt!=""){o.dypop=o.alt;o.alt=""};
if(o.title!=null && o.title!=""){o.dypop=o.title;o.title=""};
if(o.dypop!=sPop) {
sPop=o.dypop;
clearTimeout(curShow);
clearTimeout(tFadeOut);
clearTimeout(tFadeIn);
clearTimeout(tFadeWaiting);
if(sPop==null || sPop=="") {
dypopLayer.innerHTML="";
dypopLayer.style.filter="Alpha()";
dypopLayer.filters.Alpha.opacity=0;
}
else {
if(o.dyclass!=null) popStyle=o.dyclass
else popStyle="cPopText";
curShow=setTimeout("showIt()",tPopWait);
}

}
}