you should style by id as id is for unique identifier and each one should have their own id
I thought widgets always generated their own id's, but if your widgets don't have specific id's this url might be of use to you
specifically this:
<?php $args = array(
'name' => __( 'Sidebar name', 'theme_text_domain' ),
'id' => 'unique-sidebar-id',
'description' => '',
'class' => '',
'before_widget' => '<li id="%1$s" class="widget %2$s">',
'after_widget' => '</li>',
'before_title' => '<h2 class="widgettitle">',
'after_title' => '</h2>' ); ?>
%1$s should give unique id per widget
source url:
http://wordpress.org/support/topic/h...ids-or-classes