Bookmarklet to toggle red border on all elements. Good for figuring out overflow issues.

overflow-helper-bookmarklet.js

javascript:(function(){
  const outline = document.querySelector('.outline-everything-with-red');
  if(!outline){
    style = document.createElement('style');
    style.classList.add('outline-everything-with-red');
    style.appendChild(document.createTextNode('* {outline: 1px solid red;}'));
    document.head.appendChild(style);
    
    
 console.log('The following elements appear to be wider than the document.');
[].forEach.call(
  document.querySelectorAll('*'),
  function(el) {
    if (el.offsetWidth > docWidth) {
      console.log(el);
    }
  }
);
  }
  else{
    outline.remove();
  }
  var docWidth = document.documentElement.offsetWidth;
})()