Q:

Add style for plugin setting page

I have done plugin for wordpress but I want to add twitter bootstrap css style into setting page for this plugin. My idea was add this code:
function my_plugin_admin_styles() {
    wp_register_style( 'bootstrap-style', plugins_url('style/bootstrap.min.css', __FILE__) );
    wp_enqueue_style( 'bootstrap-style' );
}

if (isset($_GET['page']) && $_GET['page'] == 'my_plugin') {
    add_action( 'admin_print_styles', array($instance, 'my_plugin_admin_styles'));
}

But it effects everything and it change menu on left side too. Is possible apply css only for my setting page?

A:

You would need to create a customized CSS file that targeted only things within your section of the plugin settings page. For example, you could build the plugin settings page with a wrapper like so:
<section id="mypluginidentifier-settings">
    <!-- all the plugin settings html here -->
</section>

Then, in the CSS, just prefix everything with #mypluginidentifier-settings.
where mypluginidentifier = something unique to your plugin.
i.e. 
#mypluginidentifier-settings .button {/*button styles*/}

Otherwise you will risk conflicting with the wordpress CSS.
This is really a big hassle, though, if you want to include all of bootstrap. I would also absolutely suggest you include your CSS locally within your plugin rather than calling to the hosted version of the file (you would have to, to do this, anyway).

