free web based wysiwyg editor?

Hello,

I build a website for my parents who have no idea about html or php and they
want to change certain text sites once a month. So I started looking for a
web based wysiwyg editor and I did find some but the most of them are either
included in some kind of cms or they are thought for guestbooks they would
have to appear always on the site. I was more thinking of a password secured
directory that contains the script and when I call the script I have a
button open and can open browse for the html page to change.

Thanks for any help
Chris