a web page is inactive, after fired a desktop notification

This accurs when I use http://pomotodo.com/?debug=true

Ubuntu 12.10 amd64

firefox (Aurora 19.0a2) with "Unity Desktop Integration 2.4.1"

Expect to happen:
   1. check "Unity Desktop Intergation 2.4.1" is disabled
   2. enable "HTML Notifications 1.2" add-on
   3. Open http://pomotodo.com/?debug=true , do login first if nessesarily
   4. check Preference->"显示浏览器通知"(show desktop notifications, the latter one) is on
   5. hit the big mid button on the page and wait 5 seconds and the "0 minute" plate is highlighting and can be hit.

Use firefox (Aurora 19.0a2)，and replay the bug:
  1. check the "Unity Desktop Integration 2.4.1" add-on is enabled
  2. open http://pomotodo.com/?debug=true , do login first if nessesarily
  3. check Preference->"显示浏览器通知"(show desktop notifications, the latter one) is on
  4. hit the big mid button on the page and wait 5 seconds and the "0 minute" plate is not activated as usual.