After carrying my web application to windows server 2003 R2 from windows XP - IIS 5.1, I have encountered a ASP.Net AJAX issue that my page is performing a full page postpage instead of a partial page postback of the expected AJAX page elements.
I have searched everywhere, and this is the only solution I can find. I just stumbled upon this page below and I applied what it is saying. I would like to thank to Neil kilbride for sharing this solution with us.
I just added to my web.config file following code to solve the problem.
<xhtmlConformance mode="Transitional" />
And also he says that “ If you are having ASP.Net AJAX issues I recommend removing the <xhtmlConformance> section from your web.config file or perhaps set it to Transitional or Strict. ”