I was visiting warner brothers web site yesterday and I got a pop up with the safari compass and it said HTPP://scanner2.defender-scan.com
Your computer has been running slower than normal, it may be infected with viruses, adware or spyware. win-x-defender will perform a quick search. completely free scan.. I closed it and got off the site.
Should I be concerned?
Thanks S.b.

No. This is most likely just a pop up spam. One thing you could do though is to make sure your browser blocks pop up windows like these.
For Safari for instance, this option is available right in the "Safari" menu, or by hitting ⇧⌘K

If it downloaded anything, it will most likely be some kind of Windoze malarkey. just make sure that if you come across any "suspicious" files in your Downloads folder that you delete them. There have been some spurious .app files, perhaps malware or something, that are targetting OSX systems.

Also, if you got that - you are not at the legitimate Warner Brother's site, but rather some kind of "look alike" site, perhaps based off shore somewhere. I would be sure to Google to see what the actual address for Warner Brothers is, because a very real flaw in Unicode is that one can fiddle with the characters, so that the address may look like Warner Brothers, but it is actually something in cyrillic that lands you on a server in Tajikistan or somewhere. They will try to "hook" you into doing something, so they can use your information for criminal activities.

So you do not have to be paranoid about such things with a Mac, just be cautious and make sure that, if you doubt the characters that an address is formed with, to simply type them in yourself to make sure you go to the real site. The other thing I do is, with FireFox run the add-on called FlagFox. Warner Brothers should be American - so the little Stars and Stripes will give you piece of mind. If the flag looks like some kind of rehash of communism, or something else crazy that you don't recognize - then that should send a simple warning. This stuff is happening more and more.

If you have FireFox, you should also consider the AdBlock add-on (as well as FlashBlock) to make surfing more enjoyable. I think PithHelmet is an equivalent for Safari, but I am not sure.

No, the equivalent for Safari is Safariblock, which does both regular blocking AND Flash blocking.