There are only 3 hard rules, all else are guidelines, it is up to one who is counting, what guidelines one wants to follow.

Rule 1: Wave 2 cannot retrace more than 100% of Wave 1.

Rule 2: Wave 3 can never be the shortest of the three impulse waves.

Rule 3: Wave 4 can never overlap Wave 1.



http://stockcharts.com/school/doku.php?id=chart_school:market_analysis:elliott_wave_theory#three_rules

Corrections don't have any hard rules, just guidelines.

Here is a good site for guidelines:

http://www.tradingfives.com/articles/elliott-wave-guide.htm