the use of `%3F` in URL
<p>While moving a website - that I did not build - I have run into the use of <code>%3F</code>.</p>

<p><code>%3F</code> is the <a href="https://en.wikipedia.org/wiki/Percent-encoding" rel="noreferrer">percent-encoded</a> version of <code>?</code>.</p>

<p>It seems to be used like this a lot: </p>

<pre><code>&lt;ahref="example%3Flang=1.html"&gt;Example&lt;/a&gt;
</code></pre>

<p>when linking to a file named <code>example_lang=1.html</code>.</p>

<p>So, I replaced <code>%3F</code> with <code>_</code>, and all works again.</p>

<p>I am missing something here. The old website worked. After being moved, it no longer worked. After the replacement of <code>%3F</code> to <code>_</code>, the links worked again. Why?</p>