Yeah, I got this warning today too when I was looking up a Pokemon on there. I was like 'what happened'!? Bulbapedia is probably having a problem with their advertisements that they allow on their site, that could be causing it. This was a similar problem on a site that I go on sometimes, and the moderators and admins. fixed it.
The problem will probably fixed today or in the next few days so their is no need to worry.
Here' a Technical explanation: The first hosted network is TAKE2, which is the TNH (True Name Host) of bulbapedia.com. Google appears as the second "host" as the website, however the third, CONFLUENCE, could be using an intermediary hosted on Google's servers to redirect to their own website. All domain names referenced above have been registered within the past 10 days. This will most likely only be a problem to users if they have not modified their DNS settings using the instructions in this thread. Sadly, even if the user does this, they will still receive a warning if they attempt to browse to bulbapedia.
I think that's right.