Widget css wanting to change id per block

Hi all
I use the following code in functions.php to show widgets. I changed from div id to div class as I was getting html validation errors. Is there any way to make the first div id=X and the next div id=Y etc or do I have to use a class?
Thanks

if (function_exists(‘register_sidebars’)) {
register_sidebars(1, array(
‘before_widget’ => ‘<!— BEGIN Widget —>’,
‘before_title’ => ‘<div class=”side”><div class=”box-heading”><!— BEGIN WidgetTitle —>’,
‘after_title’ => ‘</div><!— END WidgetTitle —>’,
‘after_widget’ => ‘<!— END Widget —>’.'</div>’
));
}