What does SOTDRT/TTH/ATI mean?
Posters on FJ really love to shorten things down and give people nicknames. We have a FreeJinger specific dictionary. We also have an acronym extender (for lack of a better description). It will put a line under any of the defined terms and if you mouse over them it will give you the full descriptions. You can see this in action in the title of this FAQ.
For common internet slang and abbreviations Urban Dictionary is a good place to start looking.