I posted this topic because I'm a little confused. 1)Who is Nidhogg and Jormungand? 2)Which are the Nine Worlds?
If you know anything else, your posts are welcome.

Jorgumand is the offspring of Loki and the giantess Angrboda. The world serpent who can wrap himself around the world and reach his own tail. He and Thor have had it out at least two times. The next time they are to meet is during the Ragnarok, a Norse take on apocalyptic times. Thor and Jorgumand kill each other in one of those times that sees the established pantheon give way to a new one.

Nidhogg is a dragon who lives in Nilfhelm, the spirit underworld presided over by Hel, goddess of the dead. He feeds of the corpses that Hel throws to him. Also destined to particpate in Ragnarok alongside the undead that Hel will unleash. Other Norse legends also have Nidhogg and Thor killing each other. Strange ...

Anyway, I found this much out through a Google search. Maybe you could fill in the gaps for yourself as well.

Thank you Beren. But still the second question remains unanswered. Which exactly are the Nine Worlds? I've searched in yahoo, google, altavista and many other only to find a different version of the Nine Worlds. :(

The Nine Worlds are: Asgard, Alfheim, Vanaheim, Niflheim, Midgard, Muspelheim, Jotunheim, Svartalfheim and Hel.

More detailed info here (http://todd.reimer.com/norse/myth.html)

or you could go here
http://www.pantheon.org/areas/mythology/europe/norse/articles.html
I have found that site very informative on most mythologies you can find the arangement of the nine worlds there if you look it up.

Thank you both but I know these pages. But somewhere else Valhalla and another world was mentioned so that's why I'm confused.

In the myths, Valhalla isn't one of the nine worlds, it is a specific building located in Asgard. The other world that you may have seen mentioned is Nidavellir. In some versions Nidavellir replaces Hel as the last of the nine worlds. It is just one of those cases where everyone agrees that there are nine worlds but different people had different ideas as to what they were.

Yes, it was Nidavellir. If I'm not mistaken this is the place where dwarves lived, isn't it?

Yes, it was Nidavellir. If I'm not mistaken this is the place where dwarves lived, isn't it? That is correct.

So the right "version" of the Worlds is this BOC mentioned(Asgard, Alfheim, Vanaheim, Niflheim, Midgard, Muspelheim, Jotunheim, Svartalfheim and Hel)?

One more thing: "Elf" in Old Norse is "Alf" or "Alfar"?

For the easy question - yes Alf=Elf.

BOC's version is the most common version, whether or not that makes it the correct version is beyond my knowledge. So We have

Asgard - home to the Aesir
Alfheim - home to the light elves
Vanaheim - home to the Vanir
Niflheim - home to Nidhogg
Midgard - home to the humans
Muspelheim - home to the fire giants
Jotunheim - home of the ice giants
Svartalfheim - home to the dark elves
Hel - home to Hel and her underworld beasties
and
Nidavellir - home of the Dwarves

In some versions Hel and Niflheim are one world. In others Nidavellir or Muspelheim are excluded from the nine. Personally I think having an entire world just for Nidhogg to sit there and chew on some roots is kind of overkill so I tend to favour the Hel is not a world and Hel the godess lives in Niflheim version which frees up the needed slot to fit in both Nidavellir and Muspelheim.

You mentioned 10 worlds so you have to count Hel and Niflheim as one(like I do). ;)