AJAX :: PageMethods OnSuccess Event Didn't Work In Firefox?

i write a page method and some sort of javascript to work with that method, everything fine in any browser but firefox!

[Code]....

<input id="offcheckcid" type="button" value="بررسی کلوب آی دی" onclick="CheckCloobID('offline');" style="color: Black;"/>
function CheckCloobID(sender) {
var id;
var email;
var button;
id = $get("ctl00_ctl00_cph1_cph1_offcid");
email = $get("ctl00_ctl00_cph1_cph1_offcpe");
button = $get("offcheckcid");
button.value = "کمی تامل نمائید...";
button.disabled = true;
id.disabled = true;
email.disabled = true;
PageMethods.CheckCloobID(id.value, email.value, 'offline', OnSuccess, OnTimeout, OnFailure);
}
function OnSuccess(result) {
var results = result.split("#", 2);
if (results[0] == "Accepted") {
var price = $get("offcut");
price.innerText = "30,000- ریال";
var total = $get("offtotal");
total.innerText = "570,000 ریال";
var button = $get("offcheckcid");
button.value = "تائید شد";
}
else {
alert("...کلوب آی دی و ایمیل محرمانه وارد شده وجود ندارد یا قبلا تخفیف گرفته است");
ActivateButtons();
}
}

the problem: onsuccess event did not work in firefox, no error message displayed in firebug...