IE11 does not react to conditional comments

Question

I am using asynchronous javascript functions on my website, which are not supported by Internet Explorer 11 or lower. Therefore, I want to show a warning to IE users. To achieve this, I used the following code:

<!--[if lte IE 11]> <style type="text/css"> 
#browserWarning { display:; }
#frame { display: block; }
</style> <![endif]-->

<div id="browserWarning">
    <h1>Internet Explorer is not supported!</h1>
    Unfortunately, Internet Explorer does not support asynchronous javascript functions. Therefore, this tool can only be used with current versions of Chrome (>= 58), Firefox (>=52), Opera (>=45) and Edge (>=15). Sorry!
</div>

However, nothing happens when I open the page with internet explorer 11. I have #browserWarning set to display:none in my stylesheet. Can someone tell me what I'm doing wrong?