The hottest trend currently in web development and also in mobile development is flat design. Flat Design is a design language currently used in the creation of various graphical user interfaces. The flat design refers to a style of interface design which removes any stylistic design choices that gives the three dimensional effect and hence is focused upon the minimal use of simple elements, flat colors and typography. The designers might refer this since it allows them to make the interface designs more streamlined and efficient. Thanks to Windows Phone OS and iOS7, flat design is catching the attention of all sorts of designers.
Some flat design examples: