<p dir="auto">When you visit the Bootstrap documentation with a window to small for the docs to show the sidebar on the left, then resize your browser so it does appear, the sidebar will stay at the top of the page, and doesn't scroll down with you. Neither will it mark at which section you are.</p>
<p dir="auto">I can confirm this issue in Internet Explorer 11, Firefox 30 and Chrome 35.</p>
<p dir="auto">The following issue is reproducible with the current bootstrap docs website (e.g. <a href="http://getbootstrap.com/javascript/" rel="nofollow">http://getbootstrap.com/javascript/</a>) using Firefox 28 and Chrome 33, on Windows:</p>
<ol dir="auto">
<li>Start with a large browser window.</li>
<li>Load <a href="http://getbootstrap.com/javascript/" rel="nofollow">http://getbootstrap.com/javascript/</a></li>
<li>Decrease width of the window, so that the sidebar disappears, i.e. the affix contents menu goes to the bottom of the page (you don't see it anymore).</li>
<li>Scroll all the way down to the footer, you see the affix contents menu again.</li>
<li>Increase the window width again. At some point, the affix contents menu goes to the top again (you don't see it anymore).</li>
<li>Scroll all the way up, there it is.</li>
<li>Scroll down, the affix does not follow scroll movement anymore.</li>
</ol>