I was pulling my hair out trying to find out why and so set about looking to do some Search Engine Optimization.
It was when I was checking for broken links on the site (using xenu link checker) that I noticed my site was linking to hundreds of pages on these sites below and from thousands of pages. How long for I don’t know.
The thing is I checked and could not see this links anywhere on the website or forums on the pages where they were supposed to be. They are invisible. I also know that we do not link to these sites even once, never mind thousands of times.
It seems to be only affecting the forum. The forum is Invision Power Board, I submitted a ticket with them and they applied a patch to the forums but they do not see an issue causing the problem and have not fixed anything.
I also submitted a ticket with my web hosts and they cannot see an issue from their end, so I’m working with a programmer to determine the cause, remove the links and close the hole.
Next I will contact google with the full story so that they can take action on the offending sites and remove any black marks from our site.
I have pretty much resigned myself that when you have a popular website it will be constantly probed and prodded and looked to exploit by clever but unscrupulous people.
One positive thing at least I know the reason for the drop in google rankings.
For members you will not see or experience anything and I am told there is no risk to you using the forums as normal.
I will update you with any developments.