configuring auto complete

[Jannis]

Dear Emacs users,


i just installed autocomplete and try to configure emacs so that the 
results looks like here:

http://www.emacswiki.org/emacs/ESSAuto-complete#toc3

I have this in my .emacs:

;; autocomplete stuff
(add-to-list 'load-path "~/.emacs.d/autocomplete/")
(require 'auto-complete-config)
(add-to-list 'ac-dictionary-directories "~/.emacs.d/autocomplete//ac-dict")
(ac-config-default)
(define-key ac-completing-map [tab] 'ac-complete)


However, these nice drop down menues as in the screenshot above do not 
show up. When I press tab, possible arguments etc just show up in 
another emacs buffer. Do I need to press any particular key? Do I need 
to do any specific configuration?

In addition now a browser window is opened automatically when I 
partially type a function name until only one possibility is left. Is it 
possible to switch this off?


Cheers
Jannis