HTTP server plus CGI was designed to be a gateway to anything. HTML browser with Javascript, plugins and capability to perform HTTP GET, POST methods was design

HTTP server plus CGI was designed to be a gateway to anything. HTML browser with Javascript, plugins and capability to perform HTTP GET, POST methods was designed to be easy to be programmed. So the hard part are 1. The right UI that makes the task easy. 2. The accumulation of data and/or consturction of the system behind the HTTP server that does the task. And in case you have millions simultaneous users, you will have a lot of fun to find efficient ways to perform the task. (Efficiency in both computing resources consumptions and economical cost) 3. Building the system described in 1 and 2 fast enough to have feedback from users frequently and iterate it fast so they will always expecting something good/useful/cool shows up every now and then. 4. Good quality of service. Whether there is only one user or billions of users in the world use the system. The system shouldn't make them frustrated in complete the task. The system shouldn't waste their time in life by waiting a broken page.