While going through MSDN I found that in button properties useSubmitBeheviour there is written that if useSubmitBeheviour is true then it cause the Button control to use the browser's submit mechanism and false then the ASP.NET page framework adds client-side script to the page to post the form to the server.
What its mean? please explain it?
When you POST a form you specify the location where the form data will be sent to be processed. It can be the same page or a different page. This is determined by the value of the ACTION attribute of the FORM tag. POSTBACK posts the data back to the same page and processed.
ASP.NET page framework writes a script block to submit the form in case you are not setting useSubmitBeheviour. In case you set this, the rendered XHTML for the button makes it the submit button for the form and the submission is done. In both the cases, the submission is done.