Why is it "It is important that she do it" and not "it is important that she does it"
To me this one sounds correct - "it is important that she do it" and this sentence sounds wrong - "it is important that she does it". But I don't know the rule that makes the first sentence correct and the second one wrong. Can anyone please tell me why it is "do" and not "does"?

Question

Why is it "It is important that she do it" and not "it is important that she does it"
To me this one sounds correct -  "it is important that she do it" and this sentence sounds wrong - "it is important that she does it". But I don't know the rule that makes the first sentence correct and the second one wrong. Can anyone please tell me why it is "do" and not "does"?

Answer

It's called present subjunctive.

Basically, the action is not real but strongly wished-for.  The verb isn't conjugated at all. Using "does" means the action exists in reality.

Answer

Actually, the verb is conjugated in the subjunctive mood in sentences like this to express a strong wish, need, requirement, etc. The third person singular subjunctive of "to do" is just "do." This is also why you have sentences like "It is important that you be ready when I arrive.", "It is imperative that he come before midnight.", etc. To read more on the subjunctive mood in English, check out the Wikipedia article here: http://en.wikipedia.org/wiki/English_subjunctive