Element by Html page

Sorry for my english, but i’m italian. So, i have a problem. I have created an addon for Firefox and this addon must take an element from a google code page.

I need to take value of a textarea and show it in my popup . I have tried to use this instruction:
window.opener.document.getElementById(“text”)

but as result i have “null”. I have tried to print an alert. How can i resolve this problem??

try


window.opener.document.getElementById("text").value