Default top and bottom margin disappear in IE7

Hello fellow stylesheet colleagues,

Load this url:

http://www.gtalbot.org/BrowserBugsSe...Disappear.html

I would appreciate it if someone could explain

1- why MSIE 7 render this simple webpage so differently from Firefox
2.0.0.9, Opera 9.50, Safari 3.0.3?

2- If this is due to a bug in MSIE7? If so, which one?

3- When querying the currentStyle of margin-top and margin-bottom of
#OrdinaryPargLime with IE developer toolbar or by querying with
currentStyle.marginTop, the value returned is "auto". When creating a
nested <p> with margin declaratively set to auto inside a div with
Parent-Floated-Yellow-Div class, then the top margin and bottom margin
suddenly occur in MSIE7 but are removed in other browsers (Firefox
2.0.0.9, Opera 9.50, Safari 3.0.3).

What I am trying to say is this: in MSIE 7, the current style values
of margin-top and margin-bottom for #OrdinaryPargLime and for
#OrdinaryPargWithMarginAutoOrange are the exactly the same: auto.

4- In MSIE 7, paragraphs have default margins. Why are they removed
(at least not visible, not rendered) for #OrdinaryPargLime ?

Best regards,

Gérard