Thanks for looking
It appears to happen when you goto the site. Not everytime! Sometime it happens when a user logs in but again not always. I did think it was spam on my pc so ran search & destroy but it still happens so used my wifes laptop and it popped up again!
It's always for adult friend finder and always shows this in the url bar of the pop up window - adultfriendfinder.com/go/g106.subpop1?mustgounder=1.
I have search the view source file on my sites page but can't find whats coursing it or even where it's being called from. I've even search my site files to see if i can find something thats been changed without any result.... however i did have a problem a couple of weeks ago where the site was hacked and files were removed and altered so i think it's the remains of this.
Steve