Hey there,
Since I obviously don't know the specifics of your situation, I'll give you an answer based on generalities. I'd say that there are probably 3 possible reasons that they'd lower the position offered to you:
- They found someone they feel is more qualified for the position.
- They no longer want to fill that position.
- They simply don't feel that you currently fit the criteria, but that you might after more experience.
However, it doesn't matter why they might have offered you a lower position, I think what matters is if you'd be happy at the one currently being offered. If not, then be gutsy and ask them frankly why they offered a lower position - either you won't be hired (which you don't want) or they'll explain and you can make a more educated decision.
If you're happy with the lower position, or you feel that there's high potential to move-up, then go for it. The worst case is that it doesn't work out, which would leave you where you are now.
Please keep in mind that this is all subjective opinion - I, and no one else, should tote it as anything other than that. Good luck to you! I hope it works out for the best.