Login problem in struts

[MOHAN]

Hi to all,
Iam using struts 1.1, java 1.4.2, mysql 4. for my application.
When user clicks submit in login page, calls action "loginuser.do",
here getting values from "loginForm" and checking in DB and creating
session and storing the login values (email and name,id) in session.
After logout (session.invalidate()), when user came back using back
button and refersh the browser, it is automatically logins to that
user again with creating new session.
It is happens only when refreshing on "loginUser.do" url,
for other ".do" 's in the application, while refreshing redirects to
login page.
I found, when i refreshes the browser at "loginUser.do" it
automatically getting the user previously entered values from
loginForm and logging in again into his account by creating new
session.
I also wrote reset method in loginForm. but no use.I cant find where i
did the mistake.
How the values are coming back into loginForm?
How to rectify this.
Please help me on this issue....
Thanks in Advance

Regards,
Mohan