Adding custom classes to Views Filters (view-filters) and Content (div.view-contents) I'm using a theme that includes bootstrap. I'd like to inject class one_third into &lt;div class="view-filters"&gt; and two_third last to &lt;div class="view-content"&gt;. Is there a way to do so from any theme theme_preprocess_area?

I know I could accomplish using javascript (selecting div.view-filters and addClass()), but I think it would be most prudent to handle in perhaps the preprocessing?
Views provides a lot of .tpl files for doing just this. They are found in the /theme folder of the views module folder. The one you want is views-view.tpl.php

Simply copy views-view.tpl.php into your theme's templates folder and edit ~ line 43 to include your bootstrap classes and whatever other markup you require ;)