Where can I find the getElementById working standard?

Question

JavaScript

In general, the question is simple. Why, when adding 2 elements with the same id to a document, is the first element taken, and not the second?
PS I understand that you have to tear off your hands for this, but still ...

<font color="black"><font color="#0000ff">&lt;</font><font color="#800000">html</font><font color="#0000ff">&gt;</font><br/>
<font color="#0000ff">&lt;</font><font color="#800000">head</font><font color="#0000ff">&gt;</font><br/>
    <font color="#0000ff">&lt;</font><font color="#800000">title</font><font color="#0000ff">&gt;&lt;/</font><font color="#800000">title</font><font color="#0000ff">&gt;</font><br/>
    <font color="#0000ff">&lt;</font><font color="#800000">script</font> <font color="#ff0000">type</font><font color="#0000ff">=&quot;text/javascript&quot;</font><font color="#0000ff">&gt;</font><br/>
        <font color="#0000ff">function</font> ondivclick() {<br/>
            <font color="#0000ff">document</font>.getElementById(<font color="#A31515">&quot;place&quot;</font>).innerHTML += <font color="#A31515">&quot;1&quot;</font>;<br/>
            <font color="#0000ff">document</font>.getElementById(<font color="#A31515">&quot;place&quot;</font>).innerHTML += <font color="#A31515">&quot;2&quot;</font>;<br/>
            alert(<font color="#0000ff">document</font>.getElementById(<font color="#A31515">&quot;divid&quot;</font>).innerHTML); <font color="#008000">// тут на всех браузерах будет 1</font><br/>
        }<br/>
    <font color="#0000ff">&lt;/</font><font color="#800000">script</font><font color="#0000ff">&gt;</font><br/>
<font color="#0000ff">&lt;/</font><font color="#800000">head</font><font color="#0000ff">&gt;</font><br/>
<font color="#0000ff">&lt;</font><font color="#800000">body</font><font color="#0000ff">&gt;</font>        <br/>
    <font color="#0000ff">&lt;</font><font color="#800000">a</font> <font color="#ff0000">href</font><font color="#0000ff">=&quot;#&quot;</font> <font color="#ff0000">onclick</font><font color="#0000ff">=&quot;ondivclick()&quot;</font><font color="#0000ff">&gt;</font>Go!<font color="#0000ff">&lt;/</font><font color="#800000">a</font><font color="#0000ff">&gt;</font><br/>
    <font color="#0000ff">&lt;</font><font color="#800000">div</font> <font color="#ff0000">id</font><font color="#0000ff">=&quot;place&quot;</font><font color="#0000ff">&gt;&lt;/</font><font color="#800000">div</font><font color="#0000ff">&gt;</font><br/>
<font color="#0000ff">&lt;/</font><font color="#800000">body</font><font color="#0000ff">&gt;</font><br/>
<font color="#0000ff">&lt;/</font><font color="#800000">html</font><font color="#0000ff">&gt;</font></font><br/>
<br/>
<font color="gray">* This source code was highlighted with <a href="http://virtser.net/blog/post/source-code-highlighter.aspx"><font color="gray">Source Code Highlighter</font></a>.</font>

Answer 1

It is logical to assume that due to the fact that it is assumed that all ids in the document are unique, then when searching by id, finding it, the search stops. It makes sense to sort through the elements further if, according to the standard of the second, this cannot be.