css visual formatting context... how is this css formatted

[maddyromeo]

<div>
<div> i am some text <span> i am span </span> </div>
</div>

according to css2.1 spec..

A block container box either contains only (1) block-level boxes or (2) establishes an inline formatting context and thus contains only inline-level boxes.

as far as i know.... the inner div is a block container box that follows (2) rule..

now what is the state of outer div,, like how is it formatted when it contains a block container box i.e ( inner div).. does it create an anonymous block around inner div to satisfy the above rule (1)...

please help me...