When I run my project from Visual Studio using an aspx page that utilizes ajax modal popup extender, everything works fine with IE and Firefox as the default browsers. However, when I create an HTML file containing the code and open it by double-clicking, I encounter a script error stating "ASP.Net Ajax Client-side framework failed to load". Why does this happen when opening an HTML file but not when running the aspx page from Visual Studio? How can I resolve this issue and what is the best approach for deploying to production?
It's worth noting that I haven't made any entries related to Ajax in the Web.Config, and we are not utilizing any update panel. The aspx page uses ToolkitScriptManager. Also, there is another error message that follows - 'Sys' is undefined.