Fixed position misbehaviour in IE11

This may be way too late, but I had a similar issue with position:fixed and IE11, for a full page DIV (by specifying top: 0; bottom: 0; left: 0; right: 0;). Worked fine on Chrome, Edge, Firefox and Opera, but IE11 displayed the DIV at way under the full viewport size, and with rounded corners that seem to have inherited somehow from the parent.

Playing with the IE11 developer tools, I found an alternate option suggested as a parameter for position - "-ms-page". Using position: -ms-page sorted the issue; preceding this with position: fixed allowed the other browsers to carry on regardless.

Hope this helps others with a similar problem...

ADD this script in your page. IE fixed position scroll issue fixed.

<script>
if(navigator.userAgent.match(/Trident\/7\./)) {
  document.body.addEventListener("mousewheel", function() {
    event.preventDefault();
    var weelDelta = event.wheelDelta;
    var currentOffset = window.pageYOffset;
    window.scrollTo(0, currentOffset - weelDelta);
  });
}
</script>

Move the header outside the .shiftnav-wrap and place it above it, and apply the translateX seperately for header movement.

.shiftnav-open header{
      transform: translateX(590px);
}

It is not good idea to depend on its movement relative to the outer div.

elements with fixed positioning are fixed relative to the viewport/browser window rather than the containing element - http://www.w3.org/wiki/CSS_absolute_and_fixed_positioning

Another solution, you can use the header as absolute positioned, inside the left div #shiftnav-info.

For a quick solution add transform separately for IE, in IE only css hack.

@media screen and (-ms-high-contrast: active), (-ms-high-contrast: none) {
  .header, #bar-left{
      left: 0;
      transition: all .5s;
  }
  .shiftnav-open .header, .shiftnav-open #bar-left{
     left:590px;
  }
}