FromsAuthentication doesn't work on server

Here's my web.config code:
<authentication mode="Forms"> <forms loginUrl="Login.aspx" defaultUrl="Default.aspx" > </forms> </authentication> <authorization> <allow users="*"/> </authorization>

and in Login.cs
FormsAuthentication.RedirectFromLoginPage(TextButton1.Text, true);

It doesn't work after deployment

any suggests ??
thx for help

...