"This is not legal advice": frequently seen in conjunction with IAAL or IANAL.

Just as the sale of software without a disclaimer of warranties can sometimes leave the author liable for negligence if the software fails, dispensing incorrect legal advice can put a lawyer on the hook for malpractice, if a person later claims he was harmed by reliance on wrong advice. Instead of researching every online post to death, or refraining from participating in any informal discussions, many lawyers add TINLA or a simlar disclaimer to their posts. (This practice should not be confused with the abominable habit some mailers have of adding 15 lines of text claiming "this is a confidential communication" to posts to open listservs.)

Some non-lawyers add TINLA just to make sure.