I was looking at this timelinethis timeline for very boring, uninteresting reasons. The JS (and, consequently, responsive elements) on that page is broken.
VM3535:6 Uncaught ReferenceError: Invalid left-hand side in assignment
at eval (<anonymous>)
at http://ajax.googleapis.com/ajax/libs/jquery/1.7.1/jquery.min.js:2:11530
at Function.globalEval (http://ajax.googleapis.com/ajax/libs/jquery/1.7.1/jquery.min.js:2:11541)
at HTMLScriptElement.bp (http://ajax.googleapis.com/ajax/libs/jquery/1.7.1/jquery.min.js:2:3293)
at Function.each (http://ajax.googleapis.com/ajax/libs/jquery/1.7.1/jquery.min.js:2:11937)
at init.domManip (http://ajax.googleapis.com/ajax/libs/jquery/1.7.1/jquery.min.js:4:1920)
at init.append (http://ajax.googleapis.com/ajax/libs/jquery/1.7.1/jquery.min.js:3:31818)
at init.html (http://ajax.googleapis.com/ajax/libs/jquery/1.7.1/jquery.min.js:4:776)
at HTMLSpanElement.<anonymous> (httphttps://stackoverflow.com/admin/posts/timeline/39442238:1100:20)
at Function.each (http://ajax.googleapis.com/ajax/libs/jquery/1.7.1/jquery.min.js:2:11937)(anonymous function) @ jquery.min.js:2globalEval @ jquery.min.js:2bp @ jquery.min.js:2each @ jquery.min.js:2domManip @ jquery.min.js:4append @ jquery.min.js:3html @ jquery.min.js:4(anonymous function) @ 39442238:1100each @ jquery.min.js:2each @ jquery.min.js:2(anonymous function) @ 39442238:1098n @ jquery.min.js:2fireWith @ jquery.min.js:2ready @ jquery.min.js:2B @ jquery.min.js:2