Really simple blogging

[Mike]

I have a client who wants to add a blog to his website. Rather than adding a blog into the website that I maintain for him I thought the simplest thing to do would be for him to have an independent blog with a link to and from the main site. That way he can maintain the blog independently without having access to the main website (don't want him fiddling with that).

He has a very limited computer knowledge - just uses Word and an old version of Photoshop on a Mac.

Any recommendations for a blogging system that he can use painlessly? Preferably it would be free. It also needs to be advert-free and look reasonably professional.

Assuming I have a choice, what are the questions I should ask or things I should look out for when recommending what he should use?