HTML - Why is frameset not showing up?

Please check the js fiddle - http://jsfiddle.net/7f304y52/ The framesets are not working though correct Doctype is put, why? Can you explain what happens when incorrect doctypes are put, will the page crash or that element is discarded

<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Frameset//EN"     "http://www.w3.org/TR/html4/frameset.dtd">
<span>asdfsdf</span>

<frameset cols="25%,*,25%">
<frame src="http://www.w3schools.com/">
</frameset>
<button>asfasf</button>

Solution

You need to set correct DTD in Fiddle Options and delete your own head tag.

enter image description here