Recently I discovered the Windows 8 mail app (Touch/Metro) not playing nice with the background-size CSS property. This property is often used when you need scale down an image on the fly, one reason for doing this is for optimising image assets for high resolution devices. The Windows 8 mail app supports CSS3 and hence this can be done. However background-size doesn’t actually work in some cases and its all dependant on the way you write background CSS properties. Find out more on how to avoid this quirk below!