Some questions on the site are down voted (often quite rightly) because the scope is too large, grammar incorrect, or too little information given. However with a little editing the question may actually be quite useful. When down voting a (non-modal) box should appear asking the user if they would like to have a go at editing the question instead. This could potentially increase the volume of quality questions.
For grammar where the OP's intent can be understood it should be a case of someone editing. If the meat of the question cannot be gleamed a downvote may make more sense, and a comment requesting clarity. Editing the scope of a question can be a challenge, often when someone asks a very broad question it is a case of having not looked into solutions yet.
However, I dislike the popup as having rep to downvote implies that I have been with the site for a decent while, and for the broad case of users whom downvote, they understand the implications.
The important thing here is that they can change their vote if the question is edited. Too large of a question or not enough detail is a close vote type situation and is quickly resolved by the user correcting the question, but another user may not be able to. Poor grammar is very case by case, and although it happens, it is not very common for that to be a major case of downotes in my opinion, and would prefer not have the spam about edits.