The fat red brownish line is the Gann fan trend line from the last swing low (July 2013 at $63) to the last swing high (November 2013 at $1163).
This is the line which - surprise - happened to be the current low at $442. And it's the line where I hope Bitcoin is nearing the bottom of the current downtrend channel which started at $597. Maybe the BTC price stops falling somewhere around $460.