Create a simple API for an ASP page, to be able to use it in another HTML page

hi I have code for asp page twenty years old. I have more than twenty years code experience on development application base .net framework. hope I can help you. btw: I also worked for two Australia company more than fifteen years. I also created the biggest online canteen site base .net framework on Australia market have more than 300.000 users. peek time have more than 20,000 users place order in one hours. best regard Bill