I want to make a simple extension to the sidebar. To do this, use the template on this page:
https://www.aeyoun.com/posts/opera-sidebar-extensions.html

Standard template works fine. I've only got a link in the template, then the template is no longer anything downloaded from the Internet and displays only the white box. Tried with multiple sites.

Screenshot:
http://www.picshare.ru/view/6171985/
In the screenshot the same site is open tab in the panel.

Maybe it's the encoding format. I use Notepad ++