function determineActiveURL(callback) {
    var b = window.URL || window.webkitURL,
        tabURL, parsedURL;
    chrome.tabs.query({
        active: true,
        windowId: chrome.windows.WINDOW_ID_CURRENT
    }, function(tabs) {
      if (!tabs || tabs.length == 0 || !tabs[0].url) {
        return;
      }
      tabURL = tabs[0].url;
      parsedURL = new window.URL(tabURL);
      if (parsedURL.hostname) {
        callback(parsedURL);
      }
    })
}