<td>, <th>, <p>, <li> (Customized in this Style)

[Freesteyelz]

Unless it's a global call, you can override the CSS settings within the <div> or even <span> tags. Since the <div> in your example has an ID you can add a class attribute such as:

<div id="post_message_141" class="msgfont">

And place the CSS in Main CSS "Additional CSS Definitions" as:

.msgfont {
  font-family:verdana, helvetica, arial; /* or whatever font type you want */
  }

Or

<div id="post_message_141" style="font-family:verdana, helvetica, arial">

See if that works.