<!-- in the CSS, all <dt>'s and <dd>'s are styled "display: inline;" -->
<!-- using <span> as a grouping element -->
<dl>
  <span style="display:block">
    <dt>Firstname </dt>     <dd> $some_db_data </dd>
    <dt>Lastname </dt>      <dd> $some_db_data </dd>
  </span>

  <span style="display:block">
    <dt>Street </dt>        <dd> $some_db_data </dd>
  </span>

  <span style="display:block">
    <dt>Postal code </dt>   <dd> $some_db_data </dd>
    <dt>City </dt>          <dd> $some_db_data </dd>
  </span>
</dl>

<!-- in the CSS, all <dt>'s and <dd>'s are styled "display: inline;" -->
<!-- using correct markup, styling the last inline element beloning to a "group" with css pseudo-element :after or some other clever trick -->
<dl>
    <dt>Firstname </dt>     <dd> $some_db_data </dd>
    <dt>Lastname </dt>      <dd class="break"> $some_db_data </dd>

    <dt>Street </dt>        <dd class="break"> $some_db_data </dd>

    <dt>Postal code </dt>   <dd> $some_db_data </dd>
    <dt>City </dt>          <dd class="break"> $some_db_data </dd>
</dl>