Why and how System.Threading._TimerCallback.PerformTimerCallback(object state) event gets called?

Question

I am working on a web application. I noticed that one of my pages is getting called twice. On studying the call stack trace for this page_load event, I found that the second time page_event is called it is called from the event:

System.Threading._TimerCallback.PerformTimerCallback(object state)

I am not sure why and how this event gets called. I am using infragistics third party controls in my page.

Please note that I have already verified that page_load is not called twice because of the following reasons:

1. empty src in img tag.
2. page_load getting called from code behind as well as designer.cs.

Any help is greately appreciated.

Regards,

Hari