Use pagerequestmanager in the Response Surface of Asp.net ajax to solve the null Problem

Use ASP. NET in the original system for the first time
When using WebService APIs in Ajax, the system always prompts that pagerequestmanager is null. When using the HTML sniffing tool, the problem is that there is no automatic injection.
The microsoftajaxwebforms. js file, and the example running is not a problem, I thought it was estimated that the Web. config configuration file has been replaced.
No way, you can only find the cause for a period of time. It is found that <xhtmlconformance mode = "Legacy"/> after removing it, the file is added to normal.
Find the instructions on xhtmlconformance configuration in msdn

Value	Description
Transitional	XHTML 1.0 transitional
Strict	XHTML 1.0 strict consistency
Legacy	In order to ensure consistency, some of the presentations will be changed to V1.1.

That is to say, because in vs. net2003, the export method of some controls does not meet the XHTML standard.
<Xhtmlconformance
Mode = "Legacy"/> is set for V1.1 compatibility. After the upgrade from vs2003 to vs2005, added this role to the normal operation of the original certificate.
Point, while Asp.net
Ajax must require that your facial recognition method must comply with the XHTML standard. Otherwise, it may cause start logging, due to inconsistent standards, the container element cannot be identified at the client end.

However, I did not find any corresponding prompts. I had to know about Web. config for half a day.