Ha! While technically this phrase isn't "online jargon" because it originated in the 19th century, you will see it used often in online chat rooms.
"Bob's your uncle" is a British expression which means "everything's fine." It originated in 1877, when the British Prime Minister, Robert Cecil, appointed his nephew as Minister for Ireland. The press had a field day when he referred to the Prime Minister as "Uncle Bob." That's how "Bob's your uncle" became a popular phrase applied to sum up any positive situation.