Cannot fold drawer

[azubi <azubi@acm.org>]

Hi all,

I've recently discovered the drawers for org-mode. When I use "standard" 
drawers names (like LOGBOOK or PROPERTIES) I can fold them using the TAB 
key. If I create drawers with other names (like URLS or NOTES), these 
folders cannot be folded. I've created these specific folder using the 
function "org-insert-drawer" and therefore I suppose that I do not have 
some syntax problem, but I see that these "non-standard" drawer names 
are not "colorized" (sorry I don't know how to explain this clearly).

The version of org-mode I use is:

Org-mode version 8.2.4 (8.2.4-dist @ 
/home/azubi/.emacs.d/elpa/org-20150720/)

Can you please explain me what I've done wrong ?

Thank you in advance for your help.