There is a danger associated with this kind of “hack”. First of all, browser vendors may decide to change their security policies and mimic Opera’s behavior for example. If this happens, CrossFrame will stop working for those browsers. Furthermore, I do not recommend using hacks because they slow down the rate of innovation on the web (it makes the task of developing web browsers even more complicated than it already is, and also makes your application less maintainable) Therefore, as paradoxical as it may seem, I do not recommend using CrossFrame (or any of those ugly hacks for that matter)
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