Actually most of us think about OBJECT and EMBED tags as inseparate pair. The reality is different. In fact you don’t need to use the EMBED tag.

Only by using the OBJECT tag you ensure it will be interpreted correctly by every browser.

As you may know, the EMBED tag is supported by Gecko and WebKit, but not by IE. On the other side the OBJECT tag is supported by every one.

Why than the most common usage is with OBJECT and EMBED? That’s by me because of misunderstanding of the semantics of those two!