如何确定HTML元素是否在另一个HTML元素后面？

I have this HTML :

我有这个HTML:

HTML :

<div class="stave-container">
  <section id="Captcha"></section>
  <div id="horiz_container_outer">
     <img class="img1" />
       ...
     <img class="imgn"/>
  </div>
</div>

++++++++++++++++++++++++++++++++++++++++
+         +                            +
+#Captcha +  img | img | img | img     +
+         +  div#horiz_container_outer +
++++++++++++++++++++++++++++++++++++++++
<div