[alexeis]

структура:
/sample
-install.rdf
-chrome.manifest
/chrome
/content
-sample.xul
-main.js

install.rdf:

<?xml version="1.0"?>
<RDF xmlns="http://www.w3.org/1999/02/22-rdf-syntax-ns#"
     xmlns:em="http://www.mozilla.org/2004/em-rdf#">

  <Description about="urn:mozilla:install-manifest">
    <em:id>sample@example.net</em:id>
    <em:version>1.0</em:version>
    <em:type>2</em:type>
   
    <!-- Target Application this extension can install into, 
         with minimum and maximum supported versions. --> 
    <em:targetApplication>
      <Description>
        <em:id>{ec8030f7-c20a-464f-9b0e-13a3a9e97384}</em:id>
        <em:minVersion>1.5</em:minVersion>
        <em:maxVersion>4.0.*</em:maxVersion>
      </Description>
    </em:targetApplication>
   
    <!-- Front End MetaData -->
    <em:name>sample</em:name>
    <em:description>A test extension</em:description>
    <em:creator>Your Name Here</em:creator>
    <em:homepageURL>http://www.example.com/</em:homepageURL>
  </Description>      
</RDF>

chrome.manifest:

content sample chrome/content/
overlay chrome://browser/content/browser.xul chrome://sample/content/sample.xul

sample.xul:

<?xml version="1.0"?>
<overlay id="sample" 
         xmlns="http://www.mozilla.org/keymaster/gatekeeper/there.is.only.xul">
 <script type="application/x-javascript" src="chrome://sample/content/main.js" />
 <statusbar id="status-bar">
  <statusbarpanel id="my-panel" label="Hello, World!"  />
 </statusbar>
</overlay>

main.js:

window.addEventListener('load', foo, false);

function foo() {
alert('foo');
}

как сделать что бы alert срабатывал после каждой загрузки страницы, а то сейчас появляется только при создании нового окна