BLOCK FORMATED ELEMENTS:
1) Cause a "line return" ( visually speaking at least), for example P, DIV and BLOCK QUOTE, as opposed to A, SPAN , EM, or STRONG... wich are inline elements)
2) they can be assigned HEIGHT ( or more importantly , inline elements cannot be asigned height
3) BLOCK LEVEL can contain INLINE ( or other block level elements), but INLINE CAN ONLY CONTAIN INLINE.
4) for STYLING PURPOSES... you can make any element ( including inline) behave like a block by: floating it, giving it position:absolute; or display:block;
It will construct a anonymous block box, which is a block element to hold the inline element. However, the inline element does not become block?
I think you meant anonymous INLINE element.
As far as Paul's last post.
It is bad practice to have INLINE + BLOCK as siblings. Sometimes you will see it done ( look ate the suckerfish dropdown technique for example). So what Paul was saying was that IN THAT PARTICULAR SITUATION it becomes necessary to wrap the inline element in a block element.... at which point the inline tag COULD become redundant...
P and EM CANT be siblings... but EM does have a meaning, semantically.
is what you would then need to do IN YOUR MARK UP.
It's important to understand that BLOCK elements (or INLINE elements) can be DISPLAYED as inline ( or block) but they do not BECOME BLOCK or INLINE. So in the HTML you must follow the proper structure. use CSS afterwards to style to suit your needs.
I hope this clarifies things a lil.