I have form in my ASP.NET masterPage.master and if i click on submit it call some method from masterPage.master.cs file by ajax (i have it in update panel). But i want improve i
I did not quite get the setup you have created.
The success function is actually called with 3 parameters.
success : function( data, textStatus, jqXHR ) {
}
You can safely ignore textStatus and jqXHR and just write
success : function( data ) {
}
The data element is the result you get back from you ajax call. You can search within that data to get the desired ID.
Another option would be to create the div from jQuery with a simple insert or append call and create the id in the script. (perhaps using date and time to be unique, or just get the highest id and increase a counter) You could then just load the html to be placed into the div via a call to jquery.