Scrabmle/Encode/Decode ROT13 online - using php script.

About ROT13

ROT13 - ("ROTate by 13 places", sometimes hyphenated ROT-13, or lowercase rot13) is a simple Caesar cipher used for obscuring text by replacing each letter with the letter thirteen places down the alphabet. A becomes N, B becomes O and so on. The algorithm is used in online forums as a means of hiding joke punchlines, puzzle solutions, movie and story spoilers, and offensive materials from the casual glance. ROT13 has been described as the "Usenet equivalent of a magazine printing the answer to a quiz upside down" The name "ROT13" originated on Usenet in the early 1980s, and the method has become a de facto standard. Although a Caesar cipher, a method of encryption thousands of years old, ROT13 provides no real cryptographic security and is not used for such; in fact it is often used as the canonical example of weak encryption. Because ROT13 scrambles only letters, more complex schemes have been proposed to handle numbers and punctuation, or arbitrary binary data. ROT47 is a variant on ROT13 which, in addition to scrambling the basic letters, also treats numbers and many other characters. Instead of using the sequence A-Z as the alphabet, ROT47 uses a larger alphabet, derived from a common character encoding known as ASCII. ASCII maps letters, digits, punctuation and other special characters to numbers in the range 0-127. Viewed in ASCII, ROT13 covers the codes 65-90 and 97-122 : the upper and lower case letters respectively. ROT47 uses 94 characters instead, from ! (the exclamation mark, ASCII code 33) to ~ (the tilde, ASCII code 126), rotating them by an offset of 47. The use of a larger alphabet is intended to produce a more thorough obfuscation than that of ROT13, but ROT47 is far less widely supported.

More about ROT13 on Wikipedia