Not only froze my entire browser (ALL firefox tabs, including youtube playing in another window), but it locked up my entire system for a few seconds, I couldn'

Not only froze my entire browser (ALL firefox tabs, including youtube playing in another window), but it locked up my entire system for a few seconds, I couldn't alt-tab or anything. That's... almost impressive in how bad that is. I didn't know a website COULD lock up an entire system in this day and age.