This should be abstracted and parameterized.

```js
function error( target, file ) {
  window.console.error('Error while loading %d: %d', target, file);
}

// And later called from either `_js`:
script.addEventListener('error', function handler() { 
  error('script', script.src);
  script.removeEventListener('error', handler);
});


// ...or `_css`:
style.addEventListener('error', function handler() { 
  error('style sheet', style.href);
  style.removeEventListener('error', handler);
});


```