How to ensure nxml-mode instead of sgml-mode for html-file?

[Le TeXnicien de Surface]

hello all

I'm using emacs 22.1.1 which doesn't solve a recurring problem I have for
too long a while.

I've put that in my .emacs:

;; BEGIN
(setq auto-mode-alist
      (cons '("\\.\\(xml\\|xsl\\|ent\\|rng\\)\\'" . nxml-mode)
              auto-mode-alist))
(setq auto-mode-alist
      (cons '("\\.\\(html\\|htm\\|xhtml\\)\\'" . nxhtml-mode)
            auto-mode-alist))

(load "/home/yvon/share/emacs/autostart.el")
;; this is where I've put all of the nxml and nxhtml trees
;; I do follow the instructions of the package author
(require 'fmode)
(fmode-replace-default-mode 'xml-mode 'nxml-mode)
(fmode-replace-default-mode 'sgml-mode 'nxml-mode)
(add-hook 'nxml-mode-hook 'turn-on-auto-fill)
;; END

but so far to no avail.

When I open a 1st  html file the mode is HTML but for the 2d it is SGML
which I would like to avoid. More over, it seems that the choice of HTML or
SGML mode is quite unpredictable.

I've got no problem with xml-files for there are always open in nxml-mode.

Is there any way out of it? 
And if there is, could anybody show me the light, please.

Many thanks in advance.

-- 
Le TeXnicien de Surface