How to add events using javascript?

I have written a code in javascript to add rows to a table dynamically by clicking on to a button. I have taken values in the drop down list through database.. but it is working only for the first row.. when click on ADD row.. the event is not fired?? what is the error i am not getting that.. please help me on this...

Please attach the code that you have used. Also preferable give details of the javascript error you get when you click on the add button second time. YOou can't expect a solution with such a vague description. Also try to read How To Ask Questions.