Question: what does "Allow subframes to navigate across different domains" mean? 

Answer: This is a security setting in Internet Explorer.  (Tools, then Internet Options, then Security, then Custom Level...)\n\nThis setting gives you the option to allow IE to display subframes that originated from different domains. A subframe is a portion of a Web page that could function as a standalone page but has instead been incorporated into a larger page that may contain other subframes.\n\nYou can enable or disable this option, or you may prompt the user. Having subframes that come from different domains, however, is generally harmless and so is permitted by default.
This question from the Yahoo Q&A forum is categorized in the topic: Business & Finance