newbie: how to remove specific hgignore specification

[slalande]

I am quite new to mercurial.

I have a mercurial project that contains many restructured files which 
can be converted into html file.  So in the majority of the directory, I 
want to ignore those html file.  But for some specific directory, I want 
to include those html file in the mercurial project because they 
represent some documentation.

I know I could probably use a regexp to specify which directory I want 
to ignore those html file.  But the things is that there is too many 
directory that I want to ignore those html file.  So what I want, is to 
specify what directory that the html should not be ignored.

Is there a way to do this.

thanks.