Clearly you two are better connected and/or more experienced than I.

Rot13 is a way to obfuscate (rather than encrypt - it’s a semantic argument) text. You take the text and rotate each letter by thirteen places in the alphabet: A → N, for example. As “Hore” mentions, Rot13 is easily implemented in Unix (using a command called tr). Neither of us know why knows why tr exists, but I think it’s because tr might be (or might have been) useful for mapping from one character set to another. (Does anyone know the real utility of tr?) [Edited for Clarity]

At any rate, there was this clever little tool sitting around when people on Usenet groups (and elsewhere) decided they needed a way to tell dirty jokes or discuss plot spoilers without angering anybody. So they Rot13′d their text. If you wanted to read the joke or hear about a book’s ending, you could Rot13 the text again (therein lies the beauty of Rot13 - it’s its own inverse; 26 / 2 = 13). It was really a way of accomodating voluntary censorship; nobody cared if you wrote a dirty joke, as long as they didn’t have to see it. Additionally, Rot13 was widely used (and was a built-in feature of most news readers), so “garbled” text didn’t confuse anyone. And some people learned to just read it outright.

Now, with the HTML in full force, when people are faced with similar circumstances, they will typically make the color of a section of text the same color as the background (it can be read by selecting it - thus changing the effective background color). It’s more user friendly. It also makes the website in question look a bit ugly with all that random whitespace.

But most web browsers don’t have Rot13 buttons built in.

Anyway, you might try http://www.rot13.com as an interpreter.

Gurer ner ybgf bs jnlf bs rkcerffvat yrtvgvznpl, nffhzvat lbh rdhngr vg jvgu orvat ba gur arg sbe nn ybat gvzr (gb or ubarfg, V guvax gung lbh pna or n fryy bhg naq unir n ybat pnerre naljnl).

Bguref barf vapyqr Xvob, hfrarg (be rira hfrarg orsber gur arj tebhcf anzrf) naq ybgf bs bgure guvatf. Whfg qbag gryy zr lbh’er sebz gur Jryy.