In a web-based system I maintain at work that recently went live, it makes an Object element to embed a second web page within the main web page. (Effectively the main web page contains the menu and header, and the main application pages are in the object)
For example
<object id="contentarea" standby="loading data, please wait..."
title="loading data, please wait..." width="100%" height="53%"
type="text/html" data="MainPage.aspx"></object>
Older versions of this application use an IFRAME to do this though. I have found that by using the object tag the embedded web page behaves differently to when it was previously hosted in an IFRAME. In IE, for example, the tool tips don't seen to work (I will post a separate question about this!), and it looks like the embedded page cannot access the parent page in script, although it can if it was an IFRAME.
I am told the reason for favouring the object tag over the IFRAME is that the IFRAME is being deprecated and so cannot be relied on for future versions of browsers. Is this true though? Is it preferable to use the Object tag over the Iframe to embed web pages? Or is it likely that the IFRAME will be well-supported into the future (long after I am old and grey, and past the useful life of the application I maintain)?