Developer Suggestion:

in widgets_on_pages.php

Rather than add the CSS directly to the document head.

Enqueue it. Give other developers a little more control over where the script will load without having to edit the core files directly.

/* ===============================
  A D D    C S S    ? 
================================*/
function add_wop_css()
{
	// echo "<link rel='stylesheet' id='wop-css'  href='".get_settings('siteurl')."/wp-content/plugins/widgets-on-pages/wop.css' type='text/css' media='all' />";
	wp_register_style('wop-css', 'wp-content/plugins/widgets-on-pages/wop.css', array(), '1.0', 'all');
    wp_enqueue_style('wop-css'); // Enqueue it!
	
	}

$options = get_option('wop_options_field');
$enable_css = $options["enable_css"];
if ($enable_css) {
  //add_action('wp_head', 'add_wop_css_to_head');
  add_action( 'get_footer', 'add_wop_css' );
}