Blueprint CSS span-x in other classes

In using b开发者_StackOverflow中文版lueprint css, I have several forms in my app - for example,

<div id="user_form" class"span-15">
  ---
</div>

If I want all of my forms to have that same span, can I do something like

<div id="user_form" class="form_conainer">
  ---
</div>

and apply that span-15 in my CSS file? How would i do this?

Thanks

<div id="user_form" class="form_conainer span-15">

How about doing like this?