Your main www landing page is displaying various responsive elements in a jumble. To exclude domain issues, i took this screen on a stand alone win2008 r2 server that has never been attached to a domain.
Can confirm. Here’s a scrolling screenshot from my Win 10 EDU laptop with IE 11. No domain, screen resolution 1920x1200.
The home is making heavy use of flexbox, which has only partial support on IE11: Can I use... Support tables for HTML5, CSS3, etc
That appears to have fixed the issue. The page now displays properly in my IE11 browser, thanks.