Executable Content - HTML and XHTML: The Definitive Guide - page 741

manner, Netscape initially supported the alternative <embed> and <ap-
plet> tags for inclusion objects and later provided limited support for the
<object> tag.
All that jostling for position by the browser giants [*] made us nervous,
and we were hesitant in previous editions of this topic to even suggest
that you use <object> at all. We now heartily endorse it, based on the
strength of the HTML 4 and (particularly) XHTML standards, especially
because the currently popular browsers support <object> .
[*] Believe it or not, Netscape once dominated the browser market!
Nonetheless, be aware that the popular browsers interpret <object> and
<embed> a bit differently. For example, Internet Explorer still treats <ob-
ject> content as ActiveX controls and launches its helper program to
display the data. By contrast, the browser displays <embed> content with-
in the document display.