function getCookieVal(offset) {
    var endstr = document.cookie.indexOf (";", offset);
    if(endstr == -1) {
        endstr = document.cookie.length;
    }
    return unescape(document.cookie.substring(offset, endstr));
}
function getCookie(name){ //取某个cookie的值
var arg = name + "=";
var alen = arg.length;
var clen = document.cookie.length; 
var i = 0; 
while(i < clen)
{ 
var j = i + alen; 
if(document.cookie.substring(i, j) == arg)
{ return getCookieVal(j); } 
i = document.cookie.indexOf(" ", i) + 1; 
if(i == 0){ break; } } 
return ""; 
}