This is an abbreviation for 'Thanks in advance'
Often used in usenet but has become increasingly popular in e-mails, text messages, instant messages, chat rooms and forum posts. In fact, you could come across this abbreviation in any modern electronic communication.
An anti-plagiarism module originally developed by Dan Marsden, but was redeveloped by Turnitin, who now maintain it, as a Third Party Plugin. John McGettrick is the Lead on behalf of Turnitin.