Does this happen to anyone else?
Just lately I've been getting a black spot in some of the posts which seem to be linked to adverts.
When clicked on it either shows some links (relative to the word it is next to) or takes me directly to various sites.
Is it an update to wiki or has something been downloaded into my pc?

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ctrl and - keys to make smaller

Doesn't happen to me Degs, looks like it's your pc that has downloaded something. I tried on IE and Chrome, might be a Firefox issue though.

Derek update your explorer addons.
Ive seen this before and its a malware to do with flash not being the most upto date version.

Your stuck send me a pm I can remote connect and sort it for you.