Forms Authentication across Sub-Domains(azurewebsites.net) does not work

Form authentication with azure subdomains does not work. It is throwing back to login page. Here's code, that I am trying.

 <forms name="AuthCookie" 
      domain="azurewebsites.net"
      slidingExpiration="true" 
       loginUrl="Account/Login.aspx?timeout=yes" 
      protection="All" 
      timeout="40" 
      path="/"
      cookieless="UseCookies" />