I've been looking through the Imperial Library, and reading up on the continents of Nirn. So I have a few questions that I hope someone with a better knowledge of lore can answer:

1. In http://i48.tinypic.com/dxi63o.jpg map of Tamriel, I've highlighted two large islands that don't have any names. What are they called? Do they even have names? Also, while I can see that the one on the right is colored purple, meaning it's part of Morrowind, the other island isn't blue or purple, so it doesn't appear to be part of Skyrim or Morrowind. What's up with these islands?

2. Yokuda is definitely completely submerged, right?

3. Does Aldmeris still exist? The Imperial Library says nobody has been able to find it since the Elves left...

Aldmeris (Ehlnofey) is really the Dawn Era of existence. All the races just interpret it differently. It's not a corporeal land in the conventional sense.

Yokuda DOES still exist; its just a small archipelago now.

Concerning the map, I'm extremely confused: you highlighted two islands "without names" yet there are others on the map without names. I think you just thought about it too hard, no offense. The top right purple one is just part of Morrowind. The one on the left is Solstheim.

None taken, I just assumed the map hadn't been labeled, because unlike other islands without labels, these are fairly large. I haven't played Morrowind yet, let alone it's expansions, so I didn't even realize Solstheim existed.

I the islands owned by Morrowind on the far right are were the Telivanni are at their strongest, right? And one of them is the Indoril powerhouse of Necrom.

The one that isn't purple is Solstheim
The other ones are the Telvanni Isles, House Telvanni's isolated chief holdings
Necrom is in fact clearly displayed on the map, down the coast from the Telvanni Isles
It is not an island