It didn’t worked in my Ubuntu 11.10 box, i have found some command line solution by googling.
To make Ubuntu 11.10 to auto login gnome-shell, open up a terminal window and run this command:
raj@geeksite~Desktop/$ sudo /usr/lib/lightdm/lightdm-set-defaults -s gnome-shell
To make Ubuntu 11.10 back to Unity auto login.
raj@geeksite~Desktop/$ sudo /usr/lib/lightdm/lightdm-set-defaults -s ubuntu
To auto log-in gnome classic desktop, install gnome session fall back .
raj@geeksite~Desktop/$ sudo apt-get install gnome-session-fallback
Once installed, run the following command in terminal to enable gnome classic auto login.
raj@geeksite~Desktop/$ sudo /usr/lib/lightdm/lightdm-set-defaults -s gnome-classic
That’s All! Now you can start login without entering password in Ubuntu 11.10