I've seen other ways to go about this, but here's a nice and clean way to switch from Safari to Firefox on a misbehaving page. First, make sure you have the Safari debug menu enabled.On the Debug menu in Safari, the Open Page With menu item will list your installed browsers; assuming you have Firefox installed, you'll see an entry for Open Page With » Firefox.app. Now quit Safari, and go to the Keyboard & Mouse System Preferences panel, click on the Keyboard Shortcuts tab, and create a new keyboard shortcut. Choose Safari as the application and enter Firefox.app as the menu title. I chose Command-Option-R as my shortcut, but feel free to choose whatever you think logical. Relaunch Safari and try your new shortcut. Note the same trick works with any browser in the Open Page With sub-menu.[robg adds: On my machine, Firefox was listed without the .app extension, so...

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