Read Thread: Are links safe?
Not really. If there's a problem post, people can report it and moderators can delete it, so I'd like to think that problematic links won't last very long.
But there are steps you can take. If you're on a desktop computer and hover over the link, check where it links to. If it links to youtube.com, it's probably not going to have any porn or viruses on it.
Another thing to consider is who is posting. If it's someone with a long history on AQ in good standing, they probably aren't posting links to dangerous or inappropriate sites. If it's someone who signed up a day or two earlier.... they're pretty unvetted and it would be prudent to be a little more careful about clicking their links.
Browsers will often tell you if you try to go to a webpage known to be problematic so you have that protection as well. Either because the browser itself flags the website as suspicious or because you installed McAfee or Avast or something that will block access temporarily asking if you're sure you want to go there before taking you to the page.
But that said, for the most part, it's kind of hard for a website to do real damage just by clicking to it. I'm not saying that it's impossible, but it's not easy. They typically have to trick you into installing software, or trick you into entering private information, etc.
So for the most part, I wouldn't lose sleep over it. Even if you do accidentally click to a bad website, chances are nothing permanently bad will happen without additional steps. But say no if it asks you to download or install something, or fill out a form (especially if they ask for personal information), etc.
Thanks for your reply, Ryan. All good points, and I do feel pretty safe on AQ. 8~)