There are numerous blogs and forums discussing that “AutoComplete Extender is not working”. When I had to work on it for one of my clients, I too found that AutoComplete Extender does not work. I followed the steps given in http://ajax.asp.net/ but I was left with the same impression that “AutoComplete Extender is not working” . Anyway try try again till you get gain is the formula I generally adopt. After googling of hours together, I found the solution. Though the solution is given in many forums/blogs, yet you need to give more attention to it to catch the point. So in this blog I tried to highlight the small but the important lines that require more attention.