Hi, how do I insert a listener to Firefox http requests and responses, so that I popup a window with the address requested and the response body? Note: I have to do this building an extension to Firefox. I need a button to activate or disable the feature. For every request, I need to popup a window with an "Ok" button to allow the request to be made. Likewise, I need to popup a window with the response body from the web server, with an "Ok" button to allow the content to be displayed by the browser. I know that I have to use nsIHttpChannel, as shown here, but I don't know where to put such code on the extention's architecture. I have very little knowledge about javascript. Could anyone help me?