In Windows 8, there are two “modes” of use: Metro mode and classic mode. Metro mode sports the spiffy new UI while classic is the same old boring Windows of yore. When you run Internet Explorer 10 in Metro mode (the default) there’s a cool new feature that lets you “snap” a window to the side so you can use two simultaneously. This window, of course, is made to be far more narrow. Here’s the wrinkle: when snapped, IE10 ignores the meta viewport tag for any viewport smaller than 400 pixels in width (which it is, when in snap mode). This in turn messes up your beautifully set responsive plans and results in the same kind of smart scaling you see on non-optimized sites on an iPhone or Android device.