when i view source of your page, I see a script before the doctype tag:
if (document.location.protocol != "https:")
document.location.href = "https://www.battleoflakeerie-bicentennial.com" + document.location.pathname;
Having anything before the doctype tag will cause IE to go into quirks mode, in Quirks mode, IE uses the 5.5 rendering engine.
For IE to function properly, the first line of your page must be the doctype tag, move the script to be after the <head>