That is a browser behavior based on the user's computer. How to fix it? Only thing I can suggest is you would have to remember where the user moved it tp, set a cookie, when that window loads again check a cookie value and move it there.
I’ve looked at a lot of different solutions, and in my humble opinion Aspose is the way to go. Here’s the link: http://aspose.com
subject: Popup window position to remain constant even after backend call