define element width with blueprint, is it OK?

Question

is it wrong if I use span-x to define element width?

<div class="search span-7 prepend-17 last">
    <fieldset>
        <form action="index.php" method="get">                                  
            <input type="hidden"  name="page" value="found"/>                       
            <input class="span-4" type="text" MAXLENGTH="25" placeholder="Enter text to search" name="search"/>         
            <input class="span-3 last" type="submit" value="search" />
        </form>
    </fieldset>
</div>

Answer 1

Not at all. Span only assigns a width, float and margin. As long as this is what you want for your element there's no problem using it.