Block Site is a browser addon to help you block desired websites. To operate, simply right-click on any webpage and click on the "Block this website" context-menu item. The website will be added to the block list. Please note, the whole domain will be added to the block-list not just a URL. To change this list, open the options page and remove desired item.
For any blocked domain, you can add a redirect URL in the options page. So instead of blocking a page the website will be redirected to a desired URL.
Note: in order to report bugs, please visit addon homepage (http://mybrowseraddon.com/block-site.html) and fill the bug report form.