Well-Formedness - Refactoring HTML: Improving the Design of Existing Web Applications - page 65

Figure 3.1. An overlapping tree as interpreted by Firefox and Safari
By contrast, Opera places the second p element inside the strong element which is inside the first p element. In
essence, the Opera DOM treats the fragment as equivalent to this markup:
<p>The quick
<strong>brown fox jumped over the
<p>lazy dog.</p>
</strong>
</p>
This builds the tree shown in Figure 3.2 .
Figure 3.2. An overlapping tree as interpreted by Opera