If you ever accidentally click on a link to last measure, the key is to stay calm. If you freak out you're liable to break something or alert people surrounding you. Quickly press ctrl+alt+del and end your browser process before last measure loads completely. If you're too late for that, just turn off your computer.
There are hundreds of mirrors for last measure. The most common are anything.on.nimp.org, replacing anything with any word or any number of subdomains, and halflife2.zoy.org. The homepage of last measure is lastmeasure.com(SFW), where last measure continues to be actively developed. Last measure is released under the BSD license: it's open source and downloadable.
Person A: "Hey check out this cool site"
Person B: "Ok......god damn it you bast-HEY EVERYBODY I'M LOOKING AT GAY PORNO"