Firefox plugin - Not able to hide the tab browser

Hi,

I am developing a plugin for firefox. In which i have to open a hidden tab and access its content through javascript and close it afterwards.

Following is the code i am using for accessing content of a tab:

var newTabBrowser = gBrowser.getBrowserForTab(gBrowser.addTab("www.kayak.com/flights#/BOM-ORL/2013-05-14/2013-06-19"));
var contentdata=""; 
newTabBrowser.addEventListener("load", function () {
        contentdata=contentdata+newTabBrowser.contentDocument.body.innerHTML;
          load=load+1;
          if(load==5) {
            var DOMPars = new DOMParser();
            var dom = DOMPars.parseFromString(contentdata, "text/html");
            var priceNode=dom.getElementById('low_price');
            return priceNode.innerHTML;
    }
 }, true);

How can i hide the above tab in the browser?