Just to explain why what BPartch said works:
<img class="art_image" />
You were calling
For that to work, .art_image would have to go on it's PARENT - probably the paragraph tag you are wrapping around the image for no good reason.
<p class="art_image"><img /></p>
To that end though - christ that code is span-happy. Don't know what that bran4 class is, but fairly certain it's unneccessary since you are slapping it at EVERYTHING... The empty span preceeding it can probably be axed - you've got a class on the wrapping div so what do you even need a class on the h2 for, "small" is a presentational class and therin bad coding practice, you should have a class saying WHY it's small, not just that it's small (at that point you might as well be using a small tag), you've got a class for the images so why are you declaring align, border, etc... If that's going to be the only image inside the div you might not need a class on that (though I'd probably use a class called "trailingPlate")
I really doubt you need that section to be much more than:
Article 1 Dispelling the Myths<br />
<small>Dr Katherine Davis</small>
alt="Feeding a horse oats"
Do you buy rolled oats and feed them with chaff? Give your lazy horse oats to get him excited? Feed a bran mash once a week to help clean out his insides? Store your hay for six months before feeding it out? If so, read on - you might be surprised to learn that some of the feeding guidelines you've been following may contain more fiction than fact.
<!-- .contentPaneOpen --></div>
In terms of markup. Provides MORE than enough hooks for styling it.