Thank you for your response but I think it is more than a coincidence that two of us on the site got infected with the same bug. Perhaps we clicked on a link in a post. Could we have caught it with that?
I took this back to the dev team, and several of our developers read through all the comments on this thread. They're all confident that it's not possible these pop ups were transmitted via gardenersworld.com - it's simply a coincidence that it came up for two separate people while viewing this site. It's quite possibly a browser-related issue. Please be assured it's safe to view gardenersworld.com and that doing so won't transmit any bug or viruses to your computer.
I'm getting this popping up when I'm not on the forum, got it this pm when I was on the ngs site. I don't think it's linked to any site, just being on line will do it. I never click on anything