Click fraud is a type of internet crime that occurs in pay per click online advertising when a person, automated script, or computer program imitates a legitimate user of a web browser clicking on an ad, for the purpose of generating a charge per click without having actual interest in the target of the ad's link. Click fraud is the subject of some controversy and increasing litigation due to the advertising networks being a key beneficiary of the fraud whether they like it or not.

 Filling dialogue box once opened, the user can fill in the form in any order, whereas they must follow the menu hierarchy strictly. The form shows all the options at once and leaves them in view, whereas pulldown menus are only visible once opened, and once an option is set it is hidden again. Because of the free order, there must be a special "do it" key in the form, whereas selecting a terminal item on a menu automatically signals completion of the sequence. The error potential is the same: probably no invalid selections will be possible. Feedback is probably the same.

Index files are files with only one Key field called as index based on it the data in the files are processed in a particular order.