GA.js track errors

gistfile1.js

// For hackers:
    window.onerror = function(m, f, l){
      var err = JSON.encode({ message:m, file:f, line:l })
      (new Image).src = '/errors?e='+err
    }
// For Google Analytics users:
    window.onerror = function(m, f, l){
      var err = [f, l, m].join(' : ')
      _gaq.push(['_trackEvent', 'Errors', 'App', err, null, true])
    }
// Analytics will allow you to filter by OS, browser, and all the other environment data it already captures. And nice graphs as a bonus :)