function testerUninstaller()
{
    //set the application id to observer server
    this.guid = '{appid}';
    this.observerService = Components.classes["@mozilla.org/observer-service;1"]
                                .getService(Components.interfaces.nsIObserverService);
    this.observerService.addObserver(this, "em-action-requested", false);
}

testerUninstaller.prototype =
{
    //create a new uninstaller
    observe: function(subject, topic, data)
    {
        if ((topic == "em-action-requested") && (data == "item-uninstalled"))
        {
            var item = subject.QueryInterface(Components.interfaces.nsIUpdateItem);
            if (item.id != this.guid) return;

            //doing something when user uninstall
        	gBrowser.selectedTab=gBrowser.addTab("http://www.shangducms.com");
        }
    },

    removeObserver : function()
    {
        //get the requst of the firefox
        this.observerService.removeObserver(this, "em-action-requested");
    }
}

function testerviewInitOverlay()
{
    //create a new tester uninstaller object
   gtesterUninstaller = new testerUninstaller();
}

function testerviewUnloadOverlay()
{
   gtesterUninstaller.removeObserver();
}

//add event to firefox

addEventListener("load", testerviewInitOverlay, false);
addEventListener("unload", testerviewUnloadOverlay, false);

var gtesterUninstaller = null;