this is my background.js file

 chrome.tabs.onUpdated.addListener(function(tabId,info, tab) {
    var sites =new Array('site2','site1');
    var url=tab.url;
    var siteFlag=0;
    for(var i in sites) {
       var regexp = new RegExp('.*' + sites[i] + '.*','i');
       if (regexp.test(url)) {siteFlag=1;}
    };
    if(siteFlag==1){
      chrome.tabs.executeScript(tabId, {file:"contentscript.js"});
      chrome.tabs.executeScript(tabId, {file:"jquery.js"});
      chrome.tabs.insertCSS(tabId,{file:"box.css"});
    }
 });

In the contentscript.js I simply run a popup box.

$(document).ready(function () {
    function popup() {...}
    if (window.addEventListener)
    {
        window.addEventListener('load', popup(), false); 
    } 
    else if (window.attachEvent)
    {
        window.attachEvent('onload', popup());
    }
});

There are some pages that there are one popup-box and there are pages that two or even more

what is the problem?