Properly implementing Document forms in JavaScript could be the trickiest part in building an Ajax or JavaScript based application. The command Document enables a speedy implementation of any webpage in the client side. It is actually a command that could be implemented in the background specifying the coding language which is the coding for the client side. Basically, Document command in JavaScript is used to inform the browsers the type of programming language that will be used. This will aid the browser in properly implementing or preparing the browser so that the Ajax based application will be properly implemented. Customization on JavaScript