怎么读取客户端浏览器默认首页的地址

看看这个有用没有<html xmlns:rdl>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=gb2312">
<style>
body{margin:0px;padding:16px;background:#FFFFFF;overflow:auto;}
body,table,input,select,textarea,a{font-family:verdana,tahoma,arial;font-size:11px;color:#000000;word-break:break-all;}
table,img{border:0px;}
a{text-decoration:none;color:#003399;}
a:hover{color:#000000;text-decoration:underline;}
#id_div3{padding-top:8px;border-top:1px solid #000000;line-height:15px;}
#id_span3{font-size:10px;font-family:tahoma;}
@media all {
rdl\:homepage {behavior:url(#default#homepage);}
}
#idCodeDiv{width:100%;padding:4px;font-family:verdana,tahoma;margin:12px 0px 0px 0px;background-color:#EEEEEE;}</style>
<script>
var oHomePage,oCodeDiv,oURL;
var sHomePage;
function rdl_Verify(){
var sHomePage=oURL.value;
var bIs=oHomePage.isHomePage(sHomePage);
with (oCodeDiv) if (bIs) innerText=sHomePage+"是您的默认主页"; else innerText=sHomePage+"不是您的默认主页";
}
function rdl_Set(){
var sHomePage=oURL.value;
oHomePage.setHomePage(sHomePage);
}
function window.onload(){
oHomePage=document.all("idHomePage");
oCodeDiv=document.all("idCodeDiv");
oURL=document.all("idURL");
}
</script></head>
<body>
<rdl:homepage id="idHomePage" />
<table><tr>
<td><input type=text size=30 value="http://www.csdn.net" id=idURL></td>
<td><input type=button value=" 检测 " onclick="rdl_Verify();"></td><td><input type=button value=" 设置 " onclick="rdl_Set();"></td>
</tr></table>
<br>
<br>
<div id=idCodeDiv>请确认输入框内的url地址然后点击「检测」按钮。</div>
</body>
</html>