I recently had the opportunity to work on a project for a large company that was implementing an extensive federated search. In addition to having the search be accessible through their CRM, they wanted this search to be available on their two intranets by way of an iframe. Suffice it to say these intranets were run on pretty outdated platforms because they had to work on much older versions of Internet Explorer, which was the company standard.
My role in this project was the front-end development of the search interface. With this particular issue, I worked with the company’s back-end developers to implement the iframe into the individual intranets. We ran into a few issues, of course, when testing older versions of Internet Explorer including 9 & 10. What happened was that the meta tag on the parent page (the intranet) that sets the document mode was forcing IE to render the web page as IE8, therefore messing with the styles on the search page in the iframe.