Traditional Means of Web Application Development
In the early days the web pages were static, simple HTML web pages, later on it became dynamic by using CGI script (Perl was mostly used), Microsoft's Active Server Pages (ASP) were among the few popular languages to develop dynamic pages. But small changes in the page forced to took a round trip from the browser to server.
In the early days the application forms has to be filled and submitted to the server by pressing the submit button. After that the whole page was processed by the server and a new page sent back to browser. This causes many round trip to the server.
Early developers strove to develop a new technology to overcome this situation, at early stage the efforts were ad hoc in nature and complex too.
Traditional Web sites use synchronous techniques in which users has to wait for the response of the requests which has been made by the user and on the other hand the server has to keep waiting when user do his work.