Lots of websites use class names like floatleft, clearfloat, alignright, small, center etc that describe the
I think it depends on how you are using the styles.
Content should be named accordingly, as the style may change but the content will likely remain the same.
For instance, if you have a div that contains stock info, you should name the div something like div class="stockInfo", so that no matter what the presentation, you can change the styles and the name will not contradict those styles (as opposed to naming the div div class="yellow" and then changing the background-color to red).
However you will have "helper styles" and these should be named for what they do.
For instance, you will likely want to use a to clear some floats. In this case, it is perfectly reasonable to name it and to give it a style of br {clear:both;}.
Again, most Web sites float their images right or left. To assist with this, you can set and and then have the styles to match, img.right {float:right;} etc.
So it depends on the usage.