A Wire frame describes a web site or application using black and white lines, text and boxes. They are an extremely fast way of developing the layout, navigation and usability of a website or application. They are quick and easy to change enabling the creation of many variations at minimal cost. They can be created using anything from a pencil and piece of paper through to sophisticated software such as Auxere, Visio, Expression blend and Power point or with many free applications that are available.
The advantage of using wire frames to aid the discussion of functionality, navigation and site hierarchy is that they can be changed quickly and keep the conversation focused on the elements in question. There is no risk of a great layout being rejected due to the background being a lime green colour that no one likes. Time is not wasted discussing the font or logo. Discussions around colour and typography are extremely important but should take place separately.
Getting the wire frames right will save a great deal of time, money and effort in the long run. It is much quicker to correct an error in a wire frame than in hundreds of lines of code.
