If an element has a transparent content model, then its contents must be structured such that they would be valid HTML, even if the transparent element were removed and replaced by the child elements.
For example, the
<del>
and
<ins>
elements are transparent:
<
p
>
<
del
>
Shopping
</
del
>
<
ins
>
Returns
</
ins
>
list
</
p
>
<
ul
>
<
del
>
<
li
>
Oranges
</
li
>
<
li
>
Toilet paper
</
li
>
</
del
>
<
li
>
Toothpaste
</
li
>
</
ul
>
If those elements were removed, this fragment would still be valid HTML (if not correct English).
<
p
>
Shopping Returns list
</
p
>
<
ul
>
<
li
>
Oranges
</
li
>
<
li
>
Toilet paper
</
li
>
<
li
>
Toothpaste
</
li
>
</
ul
>