This is a good extension. I've been using it on a PC at my work for several months now without any problems. There was a glitch on my home PC at some point and I had to delete the extension because the password wouldn't pass. I'm using this extension again now.

But remember, you can bypass the extension by deleting it from the browser. So it's better to detach it from the toolbar to hide it (it's a weak protection, but better than nothing).

Thanks to the developer! This is the best I could find to prevent access to sites with personal or potentially sensitive information without installing additional software on the PC.