You Don't Need JQuery
You can basically sum up this entire rather ridiculous site with "Yes, you don't <i>need</i> jQuery, you can just use the built-in methods, but using jQuery is generally more pleasant, more consistent, and involves less typing".  One particularly egregious example from the site:<p><pre><code>  $('#foo').removeClass('bold');
</code></pre>
vs.<p><pre><code>  document.getElementById('foo').className = 
      document.getElementById('foo').className.replace(/^bold$/, '');
</code></pre>
The author summarises this, helpfully: "As usual, more characters, but still easy without jQuery."<p>Of course, if you were doing that remove class operation quite often, rather than writing all that code out each time, you might wrap it up in a helper method, and maybe you'd call it, I don't know, "removeClass" or something; perhaps if you were doing a whole bunch of DOM operations you might create little helper methods for each one, again to save you some typing.  Pretty quickly you might end up with a little library of helper methods... and, of course, being a wonderful programmer who never makes mistakes, I'm sure that little library would be every bit as optimised, reliable, and correct as a battle-tested library used on hundreds of thousands of web sites.