It looks like the neckline is at about .777 USD. The distance between the neckline and the head is .32 USD. Therefore, if the neckline support line is broken I'd expect it to go down to .777 - .32, or .457 USD before finding more support.

Source: http://stockcharts.com/school/doku.php?id=chart_school:chart_analysis:chart_patterns:head_and_shoulders_top_reversal