I am trying to open a popup window to allow a user to authenticate with twitter without having to leave the page they are viewing. I have seen this technique used around the
The popup blockers on the browser block the the popups when the code is executing in the script execution context.
E.g If we open a new window on an anchor click the popup blocker will not block it but if we try to open a new window using setTimeout you will see that popup blocker will block this. It is because when timeout is reached the context is now script execution context instead of user action. This is the same behavior when we try to open a new window in an ajax callback handler.
I think you are into similar such situation.
Live example
If for some reason you want to open the popup in ajax success handler itself then you can achieve it by making a synchronous ajax call. The popup will not be blocked.
the problem might lie in the following areas... 1. the windowSizeArray contains only a single element. 2. the code $('.twitter_popup').attr("rel") might give you some diff results than expectd because class name is used as a selector