Am I wrong about -clean

I've just started using Tidy and I'm using -clean.

I understood that on top of the indent feature, it also changes the <font>
tags to CSS and it changes the <center> tags (to what I'm not sure - am I
wrong about that?

The reason I ask is that it does neither for me - it just indents 

My line is tidy -clean filename.htm

Thanks,
David Wier
dwier@home.com