I had some site templates designed for me recently. I got the final HTML code, which validates, but the structure of the document is laid out using DL-DD pairs:
<dl>
<dd class="some-class">
Some text.
</dd>
</dl>
I'm not especially familiar with those tags as I've never used them much, but they don't seem intended for document structure. Am I right? Why would a designer do this?
From WC3: http://www.w3.org/TR/html401/struct/lists.html#h-10.3
Definition lists vary only slightly from other types of lists in that list items consist of two parts: a term and a description. The term is given by the DT element and is restricted to inline content. The description is given with a DD element that contains block-level content.
So given your example, these types of structures should be used for a specific type of content and not structuring of data that does not fit within this context.
You're right in that it shouldn't be used like that. The only reason I can think of for the designer using them is that the <dd> tag is indented in most browsers. If they're overriding the padding/margins on them, then your guess is as good as mine.
A DL tag is about the same as a UL tag, it starts an unordered list.
The difference being that there basically is no bullet in a DL/DD couple.
Most of the time, though, it's used for it's real use, that is, a Definition List, and is used with DT and DD, which are Definition Term and Definition Description which would look like :
<DL>
<DT>CSS</DT>
<DD>Cascading Style Sheet</DD>
</DL>
which will, by default, indent the term a bit, and indent it's definition a bit more.