I have heard some people miss the noon qutni when reciting and was wondering is it a major mistake to leave it?

Question
Assalaamu alaikom

I have heard some people miss the noon qutni when reciting and was wondering is it a major mistake to leave it for example recite the verse in surah al Baqarah as Khayral wasiyyahto. Does the meaning change? Please clarify this so I can advise people why never to avoid reciting it if continuing their recitation.

Answer
Wa alaikum assalam,
Baarak Allahu feekum. 
The term "noon qutni" is a term often used by some areas of the world when there is a tanween followed by a saakin letter.  The noon saakinah of the tanween then acquires a kasrah due to the forbiddance of two saakin letters meeting between two words rule.  To leave this kasrah on the noon saakinah of the tanween would be a mistake in vowels and would be counted as a major mistake.  It does not change the meaning, but a vowel mistake is a major mistake. 
Please see the following for more information on the rules of two saakin letters meeting:
http://www.abouttajweed.com/121003.htm