text: Q:
  
  Absolutely positioned drop down menu different in IE
  
  I have a dropdown menu that behaves fine everywhere (even Edge!) except for IE11.
  The dropdown menu has:
  position: absolute;
  left: auto;
  top: --nav-height;
  
  I can see that in IE11 it aligns itself to the right of the box border of Root A, which seems to indicate that it's not really absolutely positioning itself...
  The code is from this codepen but I can't get it to work at all on IE11
  All other browsers:
  
  IE11
  
  A:
  
  Try to add position:relative to the containing elements of your submenu element, in your case i think it contented in the element showing the Root A text, than you can apply left:0px to the submenu element.
  It is important to understand that a value of left:0px is set equal to the left of it's parent element, not the page.
  And setting position:relative on a the parent element sets the bounds of an absolutely positioned element equal to the parent element.
  
  