Sudden drop in my website traffic in the past 2 days!

Hello,
I experience sudden drop in my website traffic in the past 2 days, only about 20% of previous traffic!
I did a change and I think this may caused this drop and I want to confirm if adding attribute target="_blank" to internal site links in thread post may be the cause of this traffic drop and my website get penalized by google?
I've also noticed that direct traffic to my website has been decreased, traffic that come from other search engines didn't affect!

See original post by regester