The sites do display fine in the other browsers because they allow a potentially dangerous situation to go unmonitored. Opera, for security sake, does not allow an iframe from a different domain than the parent page to change the location of the parent page. This is not about it displaying correctly, it's about it following proper cross-domain protocols. I'm curious why IE and Firefox allow this to happen without so much as even a warning.
For more information on cross domain, cross frame communication, see Same origin policy
Also, from here
(on same-origin policy):
One exception to this rule is when the document.domain property is set. This exception stipulates that in an FRAME/IFRAME situation, documents served from different subdomains of the same base domain may access each other's DOM tree if both pages set their respective document.domain property to the base domain.
This doesn't happen in the capitalone.com pages, hence the fix in the original link.
Edit: Also, writing software for a Mac takes much more time to develop than writing code that works on the major web browsers. This is because Windows, Linux, Mac, and et al all mostly use their own standards and systems for compiling, interpreting, and running code. This is very good for the OS manufacturer (like Microsoft), as users who want to use a different OS, but can't find replacements for their favorite software, will probably not switch for the sake of lack of software.
Web browsers follow the same standards, which makes it easier to create cross-browser websites than it is to make cross-platform applications.
Edited by Ax238, 30 November 2007 - 02:57 PM.