Is it possible to be completely immune to certain forms of damage through resistance?

For example, I am a vampire and I was at stage three, so I had 75% resistance to frost. I also wear Nightingale Armour, which gave me a further resistance, and I believe I had something else too which further protected me.

Anyway, I think I reached what must have been 100% frost resistance. A Frost Dragon came along and his breath did no damage.

Should this be possible (want to make sure I'm not bugged) and is it possible to become immune to many forms of damage at once? Could you even become invulnerable without mods?

Yes it's possible. Enchanting helps. It's very hard to become immune to every kind of weapon though

A Breton with the Atronach Stone and a few Alteration perks becomes near immune to magical damage.

nope resists cap at 85% except for poison and disease

It's a similar effect of using Fire on a Fire Atronach. Spells have no effect on you.

Though I wonder if you can be immune to melee attacks. I haven't seen anything like that in Skyrim yet though.

Charles is right about this, there is a cap.

Also, physical damage reduction is capped at 80%, which works out to something like armor rating 567

I know you can be 100% resistant to things, but i think it has to be one singular source as other act independtly.. for example two resist frost 50% enchantments mean one makes you take half damage, and the next meant you take half that again so you can never truly get 100% with different sources of resitance. (infinistesimal i believe is the word)

However that is just a guess, based on the fact i still take poison damage despite the fact i should have more than 100% resitance

RIP Oblivion Immortal 100% Chameleon Walker:D

This. Ahhh the days of setting guards alight and then watching them run around trying to find me.

Well it's weird you say max 85% because this Frost Dragon only damaged me by biting me. If I just stood back its breath didn't touch my health at all, and I wasn't getting any regen because it was sunlight + vampire.

Magic Resistance caps at 85%
Elemental Resistance caps at 85%

Together they provide up to 97.5% protection against Fire, Frost and Shock.

But there is more,

With Atronach Stone you have 50% Chance to absorb a spell attack.
With Atronach Perk in Alteration you have 30% Chance to absorb a spell attack.
With Dragonhide Breton ability you have 50% chance to abosrb a spell attack.

If you are a Breton, and have Atronach Stone, you have once a day ability to be completely immune to all magical attacks. 50% + 50% = 100%
If you are a Vampire and have Necromage Perk, Atronach Stone, and Atronach Perk, you are completely immune to all magical attacks (50% + 30%) * 1.25 = 100%
(There is a discussion on the UESP wiki that claims that it's actually 92.5%, not 100% but I have not tried it myself. They claim the calculation should be 50% + 30% *1.25)

I made a Necromage with atronach perk and atronach stone, and can confirm its Indeed 100% spell absorbtion

Interesting, I had no idea that magic resistance stacked separately from elemental resistances.

Are you sure that the absorption stacks separately from magic resistance? Are any of these affected by difficulty setting?

Once again, Pms00 explains crap pretty thoroughly.
http://www.youtube.com/watch?v=OXyGs_yw3z4