Is it possible to use Blueprint CSS and maintain a a respectable level of separation between presentation and content? I like how easy the framework is to use when designing forms, but am worried that the manner in which I use the css classes for columnizing elements is a bad practice.

For instance, say I have a 3 field form designed using blueprint:

<div class="container">
    <form action="" method="post" class="inline">               
        <fieldset> 
            <legend>Example</legend> 
            <div class="span-3"> 
                <label for="a">Label A:</label> 
                <input type="text" class="text" id="a" name="a" > 
            </div> 
            <div class="span-2"> 
                <label for="b">Label B:</label> 
                <input type="text" class="text" id="b" name="b" > 
            </div> 
            <div class="span-3"> 
                <label for="o">Label O:</label> 
                <input type="checkbox" id="o" name="o" value="true" checked="checked" class="checkbox">checkbox one
            </div> 
            <div class="span-2 last"> 
                <input type="submit" value="submit" class="button"> 
            </div> 
        </fieldset> 
    </form> 
</div>

Is using a class attribute with names like "span-2", "inline", and "last" a bad practice? Or am I missing the point?