So i have a huge question about this movie... no, i don't want to know the meaning of the ending... i just want to know something simple because i'm really dumb =)...

Cobb's totem... it would spin forever inside someones dream, right?... so my question is: "why?" that is not a normal behavior for such an object... why would people make it spin forever in their dreams?

i would expect the totem to fall after a spinning for a while... i mean, there is normal gravity, there is normal friction...

so, what am i missing?

Why are you looking for some deeper meaning there? Inception is hardly a factually accurate movie about dreams. The totem spins forever because they said so, and the real reason is to set up the poignant final shot.

I think the real question isn't "why doesn't the top obey physics". I think the real question is "why does so much other stuff obey physics?" If it's a dream, nothing has to behave "realistically". this is shown in a few places, like the city rolling up on itself, and the zero-gravity part. To me the surprise is that there aren't more situations like that. My dreams are rarely so tame.

Nope, he's still dreaming. The end of the movie happens in limbo. The guy dies on the first level of the dream, because he's sitting in the van, which drowns, and nobody comes to rescue him. The ending is quite obviously a dream - a telling sign is the children, who are of exactly the same age and appearance as in his memories.

While I think this is probably the correct reading, I don't think it's very poignant. Consider the fact that we know Cobb has left limbo before. We're left without knowing whether he will wake up in the future and if so what will happen. Apparently killing yourself in limbo does the trick, so why doesn't he do it now? Is he unaware that he's in limbo? In which case the end is kind of a cruel trick (and we still don't know if he'll wake up and what will happen). Cobb is also defined emotionally as the movie progresses by his rejection of the simulacra of his children when originally in limbo, and the eventually even of his wife. We have no real sense that he has gone back on this, so it seems inconsistent that he would choose his children in limbo over awakening.

Basically, we're left without really knowing what this means in the broader context. If it's supposed to be something that will happen in perpetuity, which is the only satisfactory ending, then we should have some indication that he will never be leaving limbo. But we don't. Because the basic plot of the film requires Cobb (AND his wife) to have escaped limb before.

If you were in the situation in which you did not know if you were dreaming or awake, and you had a tool - the top - that would tell you, would you not check at the first safe opportunity after entering a level?
To not do so verges on insanity.

It spins forever in his dreams because he's convinced himself it does. He has just ingrained 'this is how it works' enough that if his mind can make it, it will.

Ellen Page, Ariadne, the architect. Did anyone else think this might possibly be Cobb's daughter? I think it's highly likely. They are introduced by his grandfather, who would want his son back to "reality", and supposedly she's the best he's ever seen[even better than Cobb]. It seems like something that would make an interesting theory, and generally just end up making the most sense through the whole thing. Where her goal would be to try to get her father back to "present day". So, she starts out with what most likely is the main issue behind it, the wife's death. Then continue on for whatever is attaching the father to the dream world(next the kids?). This would also explain her curiosity for Cobb, as they have more of a mentor/student -- father/daughter role.

The problem I see, is just that they never fully expanded on how long/ how buried the father is in his dreams, and the passing of time is an impossibility. But, seeing as how you are literally as old as you feel, it's quite possible the real Cobb is a lot older than shown.