ajax issue

Hi friend,
I using ajax modalpopups , on my pc and testing pc, it is working well.
After deployment on real server, all ajax controls are not working anymore, all popup can not prompt anymore.
Please tell what is root cause and how can i solve?
I just publish my project and deploy on server,
For ajax, i just add reference ajaxcontroltoolkit to my project
But now not working for ajax modalpopup.
Pls tell me how can i solve?