Human beings seem to have a number of characteristics in common. One of these well known traits is the need to be accepted or to belong to a group that is perceived as upper class, elite, limited or important. This trait is reflected in the development of Google 133t. If you haven't heard of Leet or Eleet, 133t, 1337 or 31337, chances are that you are not knowledgeable about Leetzorz, Leetspeak or 1337Z012Z either. Actually that is the point of this unusual Internet language. At one time, it was only used by a few to prevent others from understanding unless they were privy to the same signals.
Eleet was originally developed and used extensively by a group of very advanced message board posters, gamers and computer users. They used this form of written language to show that they were "elite". Since those less experienced on the Internet and in communicating using computers didn't understand the concept, the in group maintained control of the language and used it to show how inexperienced and uncool that newbies were. It is only natural that those who originally were blocked from understanding should be anxious to learn and use the language in an effort to appear as if they too were part of this knowledgeable and elite group.
The construction of 31337 is undergoing constant change as newer and more unusual words are used. It began with a simple concept. Replace the letters in your written message with other letters, numbers or symbols that look similar. It sometimes takes puzzling out the meaning, since there are variations in the symbols and there are also some words that are unique to Leet. Some words were derived from common errors made by poor keyboardists, then further changed. One common example is "teh" for "the". This word then becomes "73h".
Because the people who made the language popular tend to want to continue their elite status, an odd sequence of events has occurred. The language was created to demonstrate elite knowledge and understanding by a particular group. As the language became known to and popular with members who were not of the same level understanding, it changed the desirability of using the language. Just as many fads tend to die a natural death when "everybody is doing it", Leet is now looked upon as demonstrating ignorance of the true language of gamers, message board users and devoted computer and Internet fans.
Some common substitutions include the dollar sign "$" and the number five "5" become the letter "S". A number three "3" becomes a backward letter "E". The letter "T" is often represented as a number seven "7". More advanced forms of the language allow multiple characters to represent a single letter. For example. An "H" becomes "|-|" . The more characters in the base, the more creative Leet can become. Anything the writer can conceive and the reader can make sense of is appropriate.
There are several Leet and Haxor translators and generators on the Internet. Haxor "|-|4)(012" is another name applied to versions of the language. Some are fairly simple, while others are quite complex. You can choose the level of translation in some sites based on a percentage translated. With some more complex versions, you need to spend a lot of time deciphering the words. In fact, some versions seem to make the language confusing and hard to decipher just for the sake of being difficult to understand. You can use the translator on Google's search page to translate the page and your search words into Leetspeak.
Grammar and sentence construction is evolving so rapidly that it's hard to stay current. The rules are certainly looser than even casual English. Nouns and verbs may change places. New verb forms can appear through analogy. Misspellings are incorporated into the written forms. Because of these quirks, l337 is neither truly a language, a cipher or a dialect. Because of the rapidly changing nature of this phenomenon, it's nearly impossible to set rules that will apply in every circumstance. The characters don't just come from English character set. There are forms in Greek, Chinese and Russian languages. Some characters are borrowed from other alphabets as well.
You can use Google 133t for fun purposes. It doesn't have too many other applications except for entertainment value. One exception where Leet is useful is in the creation of user names and passwords. Because the alternative characters provide many combinations of legitimate representations, more people can have a password that is understood to be the same as another, yet when parsed through a search tool doesn't conflict.