If you’re checking out AJAX for the first time with Visual Studio 2005, and you’re using a previous created project you will have realized during your testing that AJAX doesn’t work properly. This has to do with Web.config file missing something important. Here’s the quick fix:

1. Open the Web.config file for the project.
2. Locate the <system.web> tag.
3. Add this snippet of code between that start and end tag from the previous step.

After you save the edited Web.config your AJAX should work perfectly without generating the dreaded “Sys” error. Sorry for using an image for the snippet, but it seems that the code parser doesn’t like xml/html style code.