i creating firefox extension when add this into firefox all works right but when i open a new link show a dialog box with message "Error: document body is null"

I do not think it is possible to answer this question without knowing what the extension is doing at the moment that error is generated, and on what page. Is it available for installation?

By the way, there is a better forum for your question, which is specifically for Add-on developers: https://forums.mozilla.org/addons/

Does it work with window.content.document.body?

Try to ask advice at the MozillaZine Extension Development forum.
You need to register at the mozillaZine forum site in order to post at that forum.

• http://forums.mozillazine.org/viewforum.php?f=19

my extension is for gmail page. It is installed successfully. And also woking well. but after that when we use any link it show error

Thanks for reply cor-el &jscher2000 i am not using "window.content.document.body". we send some screenshots for understanding problem i created this extension for firefox, chorme It Works fine in chrome but in firefox show error(Which have no effect on my extension or other browsing).

Your extension is designed to run on Gmail, but it generates an error on Google search results pages? Perhaps the domain filter needs to be fine-tuned so it doesn't run on that page??