Question

I want to know if I apply server side validation on a text box then when the validation event fires (I means in which state of page cycle this validation has been done in server side)

Answer 1

From this page:

Postback event handling: If the
request is a postback, control event
handlers are called. After that, the
Validate method of all validator
controls is called, which sets the
IsValid property of individual
validator controls and of the page.