Plugin – 403 forbidden to load .js file by server?

Just curious, I’ve created a little plugin to add an extra button on the TinyMCE editor but I do get a 403 forbidden by the server.

Failed to load resource: the server responded with a status of 403 (Forbidden)
wp-tinymce.php

Just included the file like this:

function gavickpro_add_tinymce_plugin($plugin_array) {
   	$plugin_array['gavickpro_tc_button'] = plugins_url( '/text-button.js', __FILE__ ); // CHANGE THE BUTTON SCRIPT HERE
   	return $plugin_array;
}

The path to the file is correctly inside my plugin folder.

Anybody know why I get this error?