Website developement problem on returning from non domain new tab.

My javascript cannot detect the difference beween closing a new preferences tab and a new non domain tab. I believe this is for security reasons. This leads to one of my custom messages popping up when closing a non domain tab, which is not standard behavour on other websites on FireFox. If the user does or does not follow the popup instructions everything works fine. My question is: does this disqualify my website from being posted to the internet for FireFox browsing, or is it tolerable to users and to Mozilla? I have intentionally left out of this post technical information about my javascript. Believe me, I have tried countless ways to code my way out of this situation but due to Firefox's strong security measures, it is impossible. I should mention that perhaps if my script was an addon I would have accesss to the TAbs API which might offer a solution. The purpose of the script is to update the website to changes to the default Browser Zoom Level as found in the prefererence settings. Does anyone know if this purpose is compatible with FireFox Addon developement?Thanks so much for directing me to informed assistance. I hope the post is not "TMI"!!