window.XMLHttpRequest undefined in IE11
<p>I am facing this strange issue with my website on Internet Explorer 11. I make Ajax call using pure JS (jquery not an option). It used to work nicely till IE10, and even with IE11 if I remember correctly, and now it won't. It happens with a lot of my users too.</p>

<pre><code>    var xmlhttp;
    alert(window.XMLHttpRequest);
    if (window.XMLHttpRequest) {
        /* IE7+, Firefox, Chrome, Opera, Safari */          
        xmlhttp = new XMLHttpRequest();
    } else { 
        alert('Inside Else');
    }
</code></pre>

<p>The above code first alerts 'undefined' and goes to else.</p>

<p>This is an intranet site. My JSPs have the <code>&lt;!doctype html&gt;</code> set, so I believe it would not trigger the compatibility view, also I am not using the <code>X-UA-Compatible</code> meta tag.</p>

<p>I have tried to uncheck the compatibility settings/enterprise mode etc, but no luck.</p>

<p>Any suggestions would be appreciated.</p>