请问这几个JS用来干什么的啊？

好复杂啊，看来看去不知道傻意思，头都大鸟:cry:

代码:

<script language="javascript" type="text/javascript">
var hm=gebid('hm');
var cp=0;
var cpre=/ CP=v=(\d+)&br=(.)/,cpv,cpbr,c=' '+d.cookie;
if(c.match(cpre)){
cp=1;
cpv=RegExp.$1;
cpbr=RegExp.$2;
if((cpbr=='i'&&cpv<60100)||(cpbr=='f'&&cpv<10001)){
cp=0;
gebid('tba').innerHTML='New';
}
}
</script>
<!--[if IE]>
<a id=ieshp></a>
<script language="javascript" type="text/javascript">
_ie=1;
var _ylh=(typeof(YLH)!='undefined')?YLH+'/':'';
var sp='http://'+location.hostname;
_ieshp=gebid("ieshp");
_ieshp.style.behavior='url(#default#homepage)';
hm.onclick=function(){var bcn=new Image;bcn.src=_ylh+"r/hz";_ieshp.setHomePage(sp);checkSHP();return false;};
hp=(_ieshp.isHomePage(sp)||_ieshp.isHomePage(sp+'/')||_ieshp.isHomePage(sp+location.pathname+location.search));
function checkSHP(){
var _hp=(_ieshp.isHomePage(sp)||_ieshp.isHomePage(sp+'/'));
if (typeof(_yc) != "undefined" && _yc.set) {_yc.set("D","","-1","/","yahoo.com");}
var bcn2=new Image;
bcn2.src=_ylh+"r/"+(_hp?"hy":"hx");
if(_hp){
shp=1;
_yc.set("HP","1","","","yahoo.com");
alert("Your home page is now Yahoo!\nThe home button of your browser goes directly to Yahoo!");
eyebrow();
}
}
</script>
<![endif]-->
<script language="javascript" type="text/javascript">
var shp=1,_hpc=_yc.get("HP"),_hlc=(_ie)?0:1;
var _hlr=(window.history.length==_hlc);
if((!_hpc&&!_hlr&&_ff)||(!hp&&_ie)){shp=0;}
else if(hp||_hlr){_yc.set("HP","1","","","yahoo.com");}
var scp=(_ie||_ffv>=parseFloat('1.0'))?cp:1;
function eyebrow(){
gebid('h').style.display=(!shp||!scp)?'block':'none';
gebid('hm').style.display=(!shp)?'block':'none';
gebid('tb').style.display=(!scp)?'block':'none';
}
eyebrow();
</script>