Should development be countable?
Some websites use developments, e.g. http://blogs.wsj.com/developments/
While others use development, e.g. http://www.un.org/en/development/
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The singular form suggests a broad process e.g. 'the development of Man from ape to space traveller', which may include 'individual developments in technology like the invention of the wheel or written language.
They both constitute acceptable usage but your examples illustrate the word being used as a noun (to refer to individual developments) and a verb (to develop, development work done generally by the UN).
In the URLs given as examples, development and developments end up mapping to a directory on a server. Whilst there's nothing stopping you using singular or plural, it makes more sense to put any newly developed work in a directory named development. This is because all kinds of developments are put there and it's overarchingly all just development work.