Guidance on dealing with a lot of data elements

I am trying to come up with a user-friendly design to convert an Access form that has a lot of data elements into a web form.  The form being converted has the following major elements to it:
Main form with about 20 data elementsSubform 1 with about 25 data elementsMany child records per main data recordSubform 2 with about 20 data elementsMany child records per main data recordSystem users are accustomed to viewing this all in one really cramped form.  My goal is to convert this into a web form that will seem familiar to them, be less cramped and allow them to work just as easily as if they were in MS Access .  It is a tall order, I know.
What have you guys come up with to deal with these situations where you have a large amount of data e ...