[TYPO3] real url + set and remove parameter

[PEF]

My website uses two templates - one for normal view and one for 
text-only view. When viewing in normal mode, I want a button to switch 
to text-only-mode and vice versa.

At this point I've got my buttons, but the urls aren't correct:
- in normal mode:
   - http://www.domain.dk/om-denne-side/?alt=1 (ok)
- in text-only mode:
   - http://www.domain.dk/alt/om-denne-side/?alt=0 (not ok)

In the latter, the alt-param following the domain, prevent the mode from 
returning to normal-mode, despite the &alt=0.

Further more: It would be nice, if the two links looks like this:
- http://www.domain.dk/alt/om-denne-side
- http://www.domain.dk/om-denne-side

In the real-url-section:preVars of localconf i've added this:
array (
	'GETvar' => 'alt',
	'valueMap' => array (
		'alt' => '1',
		'' => '0',
		),
	'noMatch' => 'bypass',
),

which only seems to be working partly.

Anyone with a solution?

Regards
Peter Falk