What do you do when you start laughing uncontrollably at work?

I discovered textsfromlastnight.com and I just stumbled over one that has me practically howling, but I’m at work. Those of you that take to reading non-work related websites at your job, how do you most efficiently stifle yourself during a guffaw?

Have you ever been caught and had to try to explain what you were laughing at without admitting you were browsing the internet?

And what do you do you if your work phone rings? :)