Why firefox shows <object> and internet explorer shows <iframe> ?

Question

Why if i use <object> in place for <iframe>, but IE shows <iframe> in rendered source.

Answer 1

I don't have IE available to look right now but IE may be getting confused because you are using the XHTML1.1 doctype. Not only does IE not understand XHTML but you are 1) serving it as HTML and 2) version 1.1 is an XML only application. That's not counting the several errors the validator shows.

Answer 2

The server must check the User-Agent header that the browser sends with its request. The server uses iframe if it looks like an Internet Explorer user-agent, and object for everything else (including Firefox, Chrome, and wget).

I confirmed that the browsers weren't somehow changing the code themselves by using wget and altering only its --user-agent argument.

As for exactly where or why the server is doing this, I can't say.