Hello Hitch,
Yes, that's how it's typed.
As far as I know it's a standard method of applying multiple CSS declarations. I use it all the time.
Here are a few examples from my latest e-book:
<div class="breakbefore breakafter"> applies page breaks around chapters
<div class="pullquote quote-bg"> applies a pull-quote text and background
<p class="first greybx"> sets no indent for first line and puts para in a grey background box
I've had no problems applying up to 5 CSS declarations to one tag.
Anyway, what about my code? Should it have worked the way I thought or is it necessary to repeat the whole font declaration just to add another selector?
Should the <div class="letter marg"> have worked?
Tony