> I have never really understood the difference between the pronounciation
> of the runes "ár" and "áss". Could you please tell me what the real
> difference is.

The theory goes that "ár" represented non-nasal 'a'
whereas "áss" represented nasal 'a'. The sources,
however, don't show this as clearly as one might
have wished.

The most thorough treatment I've read of this
is "A-rúnir í frumnorrænum rúnaáletrunum",
a 1998 B.A. treatise by one Embla Ýr Bárudóttir
(as an aside, "Bárudóttir" is a matronym,
a relatively rare thing).

> There don´t seem to be any difference between these two
> sounds in the normalized language we are using.

Old Norse had long nasal vowel phonemes which are not
marked in the normalized orthography. The best source
on this is the First Grammatical Treatise.

Kveðja,
Haukur