Users - how to enable folder deleting

Hi, sorry if this topic's already here, I couldn't find it in a search.

I have set up a couple of colleagues as 'Users' and created a 'User group' to give them particular permissions.
I have enables them to change 'Articles' but when they log in, they only have theability to delete some of the articles (see 2 attached jpegs) some have red crosses some don't e.g. 'home' 'news' 'contact'
I thought I had selected to be able to delete files (settings screen snap also attached) so how do I change this?

Thanks
Corrie

Found it!
I didn't realise I could 'Assign Access Rights' in the Site structure.

Hope this is still useful for someone else
Corrie

Files and Pages are not the same thing.