Pop-up windows really un-usable?

Not always ! not if they meet certain criteria

1. Inform user that one would open when the hyperlink element is clicked
2. Once open, force user to finish task presented in the child pop-up window before jumping back to parent.
3. Child window must be smaller than parent window
4. Keep parent window visible in the background and block all interaction when child window is still open
5. Both windows would act togther during minimise/maximise/close.

I have always needed them and used them mostly on complex internet Applications where you are left with no choice.
The best way to handle pop-up windows (and still maintain a level of usability) in such cases is to make them modal.

Development criteria:

1. it needs to be developed such that unless the pop-up (modal window) is closed the user should not be able to work on the parent window.
2. the the pop-up (modal window) would minimise/maximize/close along with the parent window
3. the pop-up (modal window) Should not show up on the task bar as a seperate window.
4. ensure cross browser compatibility.

Reference:

• http://www.codestore.net/store.nsf/unid/DOMM-4R5MDQ?
• http://www.dannyg.com/support/modalFix.html

Day to day Example: Hotmail and yahoo both use these kind of pop-up with customized HTML content when deleating 'all mails' in the 'Trash'.

Dont's: Interaction between model windows are not recomended.