I was looking for an answer, but could not find anything helpfull yet.
I have a gridview with some data (from SQL database) and an option to delete a row. Before deleting the row I want the user to confirm the delete (pupup window). I know how to create a popup with javascript, but I don’t like the apperance of that popup. I would like to make ky own “popup”.
I was thinking of overlaying one panel (where I put text (Label) and some buttons (OK, Cancel)) over the panel where I have the gridview. Something like in the picture. How would I accomplish something like that?

How about using the Ajax control toolkit popup?
http://www.asp.net/ajaxlibrary/act_Popup.ashx
This seems to do exactly what you are looking for for you.