How do you style numbered comments in an external stylesheet?

Let's say I have this:

<span id="comment-<?php echo $id; ?>" style="text-decoration:none">

Code (markup):

How could I move that style into an external stylesheet when each comment has a unique ID number, e.g. comment-1, comment-2, etc. Is it even possible?

Thanks!

EDIT: I found out elsewhere that the "id" is used for anchor links, so I'd need a class="comment" for styling.

 

<div id="box">
<span id="comment-<?php echo $id; ?>" style="text-decoration:none">
</div>

Code (markup):

Just to make it more specific you can include the div it's in, I put it in #box for the example.

#box span {
text-decoration:none
}

Code (markup):

 

That would work, too. Thanks!