Mac Virus?

[Olivio]

Every time I go into a different category here I'm plagued by large popup windows from allegedly apple sayin

"There is no application set to open the URL undefined://undefined.undefined.undefined/undefined/undefined.undefined/s/undefined/delivery.platform.switchads.com/adserver/meta_web.php?zone_id=1174&instance_id=2."

With a "Cancel" "Choose Application" and "Search Ap Store" tab at the bottom and that smug blue and white "Finder" face you usually find at the bottom of the mac tool bar

This appears about 3 times and each time a click the cancel tab more appears.

What's wrong with my computer as this has never happened before.

Thanks in advance.

[Buenchico]

I normally hate it when someone replies to a question here with 'Try googling it' but, on this occasion, I'm going to suggest exactly that (or, rather, I'll provide a link which does the job for you anyway):
http://lmgtfy.com/?q=mac+there+is+no+application+set+to+open+the+URL

That's because there are lots of similar threads there but I don't know which one (if any) will actually help you.

However, looking through them suggests that it's likely to be an error thrown up by a Safari extension. In particular, there's a suggestion that extensions which are designed to save Youtube videos (or similar) are likely to cause the problem. So, if you've got such an extension, try disabling/removing it.

(Please accept my apologies if this post simply wastes your time. I don't use a Mac, so I'm fumbling in the dark, but it seemed silly not to post a reply which might possibly help you).