Hide Parent and child category form the sidebar

HI

In the sidebar where I have a list of all my categories, that works fine. Now I would like to create a blog for FAQ, I have grouped the category in a Parent call FAQ and child category for each subject.

I don't want the FAQ parent and child categories to be shown in my sidebar widgets category list. Is there a filter or CSS code I can use to hide a specific parent/child category ??

Kennet