Want to build a website that is close to reality? You can surely go for a three dimensional interface. Add drop shadows, textures, gradients and all. But are you aware that not this dynamic design, but something else is the in-thing of web design these days? You know what it is? The flat user interface (UI) design – one of the simplest yet engaging forms of website designing styles is in vogue. Today we'll be going through 5 Common Flat UI Design Mistakes to Avoid.