Virus…? Tons of people talking. Not sure where else to ask

I really wasn't sure where to ask this, here, gaming, stack overflow, it can fit into any of them but I'll post it here. Sorry if I'm posting in the wrong area.

I was playing Half-Life just now and went to look up what a certain console cvar did via Steam's in-game browser. I clicked on a relevant result and after reading for a couple seconds millions of voices started pouring through my headphones. I couldn't understand what any of them were saying but that's irrelevant.

This happened out of nowhere after doing nothing more than clicking the first result for a Google search in Steam's in-game browser. It scared me senseless, I threw off my headphones, immediately killed the game and shut down my computer.

I booted back up with no problems and ran a quick scan via Malwarebytes and it found nothing. When I visit this page on my Firefox (AdBlock Plus + NoScript) setup it's perfectly safe and I even had a friend visit the page with internet explorer and nothing happened to him other than a browser crash.

This is my first build. I spent a lot of money on it. I cherish it infinitely and spend a great deal of my life using it. I'm pretty shook up and I'm not sure what to think about this or what sort of action to take and that's what leads me here. I'm not a serious programmer but I am familiar with programming. All I want to know is what the hell that was, what I should do, and what I should not do. Thank you in advance.

PS: I'm thinking it was some sort of javascript exploit because, as I said, I run NoScript AND AdBlock Plus on my Firefox installation and I can visit the page like it's any other. I will link to the page and also give the source if it will help. The best way I can describe it is what you hear when you type "soundchaosdebug" into chat in Diablo II.

WARNING, POTENTIALLY UNSAFE LINK! DO NOT CLICK WITHOUT PROPER PROTECTION!

http:[unsafe]//www.opensubscriber.com/message/hlds@list.valvesoftware.com/5016556.html

WARNING, POTENTIALLY UNSAFE LINK! DO NOT CLICK WITHOUT PROPER PROTECTION!