Three Questions ---- Help

Hello Everybody

Q1. Negative float: Just a fundamental question that I had. What does it actually mean to have negative (-ve) float in the schedule? Does it mean that artificially somebody has constrained activities? Does it mean that what the schedule is telling us is that it is impossible to achieve our schedule before we begin??

Q2. Planning Units: It looks as if working in "days" is the way to go (gives greatest flexibility). But i would like to display in weeks or months actually in the schedule. Is there a way to build the schedule with days but display only weeks or months?

Q3. Sorting: Is there a way to sort the schedule by start times, but for only each section of the schedule, so that the each section is in order of time but that other areas of the work breakdown structure embedded in the schedule can be independent of this? Not sure I explain Q3 very well.

Thanks for any assistance......