As of 21 May 2016, clicking "edit" on the en.Wikipedia Mediawiki instance shows the text for editing, but then overlays it with a model text box saying:

"Welcome to Wikipedia

Anyone can edit, and every improvement helps.
Thank you for helping the world discover more!"

This modal pop-up has no obvious close or "[X]" option. Ideally if it *must* be shown then there should be an obvious action-free closure mechanism such as an 'X' in the corner.